The Language of Algebra
9 Evaluate, Simplify, and Translate Expressions
Learning Objectives
By the end of this section, you will be able to:
 Evaluate algebraic expressions
 Identify terms, coefficients, and like terms
 Simplify expressions by combining like terms
 Translate word phrases to algebraic expressions
Before you get started, take this readiness quiz.
Evaluate Algebraic Expressions
In the last section, we simplified expressions using the order of operations. In this section, we’ll evaluate expressions—again following the order of operations.
To evaluate an algebraic expression means to find the value of the expression when the variable is replaced by a given number. To evaluate an expression, we substitute the given number for the variable in the expression and then simplify the expression using the order of operations.
Evaluate when
 ⓐ
 ⓑ
ⓐ To evaluate, substitute for in the expression, and then simplify.
Substitute.  
Add. 
When the expression has a value of
ⓑ To evaluate, substitute for in the expression, and then simplify.
Substitute.  
Add. 
When the expression has a value of
Notice that we got different results for parts ⓐ and ⓑ even though we started with the same expression. This is because the values used for were different. When we evaluate an expression, the value varies depending on the value used for the variable.
Evaluate:
 ⓐ
 ⓑ
 ⓐ 10
 ⓑ 19
Evaluate:
 ⓐ
 ⓑ
 ⓐ 4
 ⓑ 12
Evaluate
 ⓐ
 ⓑ
Remember means times so means times
ⓐ To evaluate the expression when we substitute for and then simplify.
Multiply.  
Subtract. 
ⓑ To evaluate the expression when we substitute for and then simplify.
Multiply.  
Subtract. 
Notice that in part ⓐ that we wrote and in part ⓑ we wrote Both the dot and the parentheses tell us to multiply.
Evaluate:
 ⓐ
 ⓑ
 ⓐ 13
 ⓑ 5
Evaluate:
 ⓐ
 ⓑ
 ⓐ 8
 ⓑ 16
Evaluate when
We substitute for and then simplify the expression.
Use the definition of exponent.  
Multiply. 
When the expression has a value of
Evaluate:
64
Evaluate:
216
In this expression, the variable is an exponent.
Use the definition of exponent.  
Multiply. 
When the expression has a value of
Evaluate:
64
Evaluate:
81
This expression contains two variables, so we must make two substitutions.
Multiply.  
Add and subtract left to right. 
When and the expression has a value of
Evaluate:
33
Evaluate:
10
We need to be careful when an expression has a variable with an exponent. In this expression, means and is different from the expression which means
Simplify .  
Multiply.  
Add. 
Evaluate:
40
Evaluate:
9
Identify Terms, Coefficients, and Like Terms
Algebraic expressions are made up of terms. A term is a constant or the product of a constant and one or more variables. Some examples of terms are
The constant that multiplies the variable(s) in a term is called the coefficient. We can think of the coefficient as the number in front of the variable. The coefficient of the term is When we write the coefficient is since (Figure) gives the coefficients for each of the terms in the left column.
Term  Coefficient 

An algebraic expression may consist of one or more terms added or subtracted. In this chapter, we will only work with terms that are added together. (Figure) gives some examples of algebraic expressions with various numbers of terms. Notice that we include the operation before a term with it.
Expression  Terms 

Identify each term in the expression Then identify the coefficient of each term.
The expression has four terms. They are and
The coefficient of is
The coefficient of is
Remember that if no number is written before a variable, the coefficient is So the coefficient of is
The coefficient of a constant is the constant, so the coefficient of is
Identify all terms in the given expression, and their coefficients:
The terms are 4x, 3b, and 2. The coefficients are 4, 3, and 2.
Identify all terms in the given expression, and their coefficients:
The terms are 9a, 13a^{2}, and a^{3}, The coefficients are 9, 13, and 1.
Some terms share common traits. Look at the following terms. Which ones seem to have traits in common?
Which of these terms are like terms?
 The terms and are both constant terms.
 The terms and are both terms with
 The terms and both have
Terms are called like terms if they have the same variables and exponents. All constant terms are also like terms. So among the terms
Terms that are either constants or have the same variables with the same exponents are like terms.
Identify the like terms:
 ⓐ
 ⓑ
ⓐ
Look at the variables and exponents. The expression contains and constants.
The terms and are like terms because they both have
The terms and are like terms because they both have
The terms and are like terms because they are both constants.
The term does not have any like terms in this list since no other terms have the variable raised to the power of
ⓑ
Look at the variables and exponents. The expression contains the terms
The terms and are like terms because they both have
The terms are like terms because they all have
The term has no like terms in the given expression because no other terms contain the two variables
Identify the like terms in the list or the expression:
9, 15; 2x^{3} and 8x^{3}, y^{2}, and 11y^{2}
Identify the like terms in the list or the expression:
4x^{3} and 6x^{3}; 8x^{2} and 3x^{2}; 19 and 24
Simplify Expressions by Combining Like Terms
We can simplify an expression by combining the like terms. What do you think would simplify to? If you thought you would be right!
We can see why this works by writing both terms as addition problems.
Add the coefficients and keep the same variable. It doesn’t matter what is. If you have of something and add more of the same thing, the result is of them. For example, oranges plus oranges is oranges. We will discuss the mathematical properties behind this later.
The expression has only two terms. When an expression contains more terms, it may be helpful to rearrange the terms so that like terms are together. The Commutative Property of Addition says that we can change the order of addends without changing the sum. So we could rearrange the following expression before combining like terms.
Now it is easier to see the like terms to be combined.
 Identify like terms.
 Rearrange the expression so like terms are together.
 Add the coefficients of the like terms.
Simplify the expression:
Identify the like terms.  
Rearrange the expression, so the like terms are together.  
Add the coefficients of the like terms.  
The original expression is simplified to… 
Simplify:
16x + 17
Simplify:
17y + 7
Simplify the expression:
Identify the like terms.  
Rearrange the expression so like terms are together.  
Add the coefficients of the like terms. 
These are not like terms and cannot be combined. So is in simplest form.
Simplify:
4x^{2} + 14x
Simplify:
12y^{2} + 15y
Translate Words to Algebraic Expressions
In the previous section, we listed many operation symbols that are used in algebra, and then we translated expressions and equations into word phrases and sentences. Now we’ll reverse the process and translate word phrases into algebraic expressions. The symbols and variables we’ve talked about will help us do that. They are summarized in (Figure).
Operation  Phrase  Expression 

Addition  plus the sum of and increased by more than the total of and added to 

Subtraction  minus the difference of and subtracted from decreased by less than 

Multiplication  times the product of and 
, , , 
Division  divided by the quotient of and the ratio of and divided into 
, , , 
Look closely at these phrases using the four operations:
 the sum of and
 the difference of and
 the product of and
 the quotient of and
Each phrase tells you to operate on two numbers. Look for the words of and and to find the numbers.
Translate each word phrase into an algebraic expression:
 ⓐ the difference of and
 ⓑ the quotient of and
ⓐ The key word is difference, which tells us the operation is subtraction. Look for the words of and and to find the numbers to subtract.
ⓑ The key word is quotient, which tells us the operation is division.
This can also be written as
Translate the given word phrase into an algebraic expression:
 ⓐ the difference of and
 ⓑ the quotient of and
 ⓐ 47 − 41
 ⓑ 5x ÷ 2
Translate the given word phrase into an algebraic expression:
 ⓐ the sum of and
 ⓑ the product of and
 ⓐ 17 + 19
 ⓑ 7x
How old will you be in eight years? What age is eight more years than your age now? Did you add to your present age? Eight more than means eight added to your present age.
How old were you seven years ago? This is seven years less than your age now. You subtract from your present age. Seven less than means seven subtracted from your present age.
Translate each word phrase into an algebraic expression:
 ⓐ Eight more than
 ⓑ Seven less than
ⓐ The key words are more than. They tell us the operation is addition. More than means “added to”.
ⓑ The key words are less than. They tell us the operation is subtraction. Less than means “subtracted from”.
Translate each word phrase into an algebraic expression:
 ⓐ Eleven more than
 ⓑ Fourteen less than
 ⓐx + 11
 ⓑ 11a − 14
Translate each word phrase into an algebraic expression:
 ⓐ more than
 ⓑ less than
 ⓐj + 19
 ⓑ 2x − 21
Translate each word phrase into an algebraic expression:
 ⓐ five times the sum of and
 ⓑ the sum of five times and
ⓐ There are two operation words: times tells us to multiply and sum tells us to add. Because we are multiplying times the sum, we need parentheses around the sum of and
five times the sum of and
ⓑ To take a sum, we look for the words of and and to see what is being added. Here we are taking the sum of five times and
the sum of five times and
Notice how the use of parentheses changes the result. In part ⓐ, we add first and in part ⓑ, we multiply first.
Translate the word phrase into an algebraic expression:
 ⓐ four times the sum of and
 ⓑ the sum of four times and
 ⓐ 4(p + q)
 ⓐ 4p + q
Translate the word phrase into an algebraic expression:
 ⓐ the difference of two times
 ⓑ two times the difference of
 ⓐ 2x − 8
 ⓑ 2(x − 8)
Later in this course, we’ll apply our skills in algebra to solving equations. We’ll usually start by translating a word phrase to an algebraic expression. We’ll need to be clear about what the expression will represent. We’ll see how to do this in the next two examples.
The height of a rectangular window is inches less than the width. Let represent the width of the window. Write an expression for the height of the window.
Write a phrase about the height.  less than the width 
Substitute for the width.  less than 
Rewrite ‘less than’ as ‘subtracted from’.  subtracted from 
Translate the phrase into algebra. 
The length of a rectangle is inches less than the width. Let represent the width of the rectangle. Write an expression for the length of the rectangle.
w − 5
The width of a rectangle is meters greater than the length. Let represent the length of the rectangle. Write an expression for the width of the rectangle.
l + 2
Blanca has dimes and quarters in her purse. The number of dimes is less than times the number of quarters. Let represent the number of quarters. Write an expression for the number of dimes.
Write a phrase about the number of dimes.  two less than five times the number of quarters 
Substitute for the number of quarters.  less than five times 
Translate times .  less than 
Translate the phrase into algebra. 
Geoffrey has dimes and quarters in his pocket. The number of dimes is seven less than six times the number of quarters. Let represent the number of quarters. Write an expression for the number of dimes.
6q − 7
Lauren has dimes and nickels in her purse. The number of dimes is eight more than four times the number of nickels. Let represent the number of nickels. Write an expression for the number of dimes.
4n + 8
Key Concepts
 Combine like terms.
 Identify like terms.
 Rearrange the expression so like terms are together.
 Add the coefficients of the like terms
Practice Makes Perfect
Evaluate Algebraic Expressions
In the following exercises, evaluate the expression for the given value.
22
26
144
32
27
21
41
9
225
73
54
Identify Terms, Coefficients, and Like Terms
In the following exercises, list the terms in the given expression.
15x^{2}, 6x, 2
10y^{3}, y, 2
In the following exercises, identify the coefficient of the given term.
8
5
In the following exercises, identify all sets of like terms.
x^{3}, 8x^{3} and 14, 5
16ab and 4ab; 16b^{2} and 9b^{2}
Simplify Expressions by Combining Like Terms
In the following exercises, simplify the given expression by combining like terms.
13x
26a
7c
12x + 8
10u + 3
12p + 10
22a + 1
17x^{2} + 20x + 16
Translate English Phrases into Algebraic Expressions
In the following exercises, translate the given word phrase into an algebraic expression.
The sum of 8 and 12
8 + 12
The sum of 9 and 1
The difference of 14 and 9
14 − 9
8 less than 19
The product of 9 and 7
9 ⋅ 7
The product of 8 and 7
The quotient of 36 and 9
36 ÷ 9
The quotient of 42 and 7
The difference of and
x − 4
less than
The product of and
6y
The product of and
The sum of and
8x + 3x
The sum of and
The quotient of and
The quotient of and
Eight times the difference of and nine
8 (y − 9)
Seven times the difference of and one
Five times the sum of and
5 (x + y)
Nine times five less than twice
In the following exercises, write an algebraic expression.
Adele bought a skirt and a blouse. The skirt cost more than the blouse. Let represent the cost of the blouse. Write an expression for the cost of the skirt.
b + 15
Eric has rock and classical CDs in his car. The number of rock CDs is more than the number of classical CDs. Let represent the number of classical CDs. Write an expression for the number of rock CDs.
The number of girls in a secondgrade class is less than the number of boys. Let represent the number of boys. Write an expression for the number of girls.
b − 4
Marcella has fewer male cousins than female cousins. Let represent the number of female cousins. Write an expression for the number of boy cousins.
Greg has nickels and pennies in his pocket. The number of pennies is seven less than twice the number of nickels. Let represent the number of nickels. Write an expression for the number of pennies.
2n − 7
Jeannette has and bills in her wallet. The number of fives is three more than six times the number of tens. Let represent the number of tens. Write an expression for the number of fives.
Everyday Math
In the following exercises, use algebraic expressions to solve the problem.
Car insurance Justin’s car insurance has a deductible per incident. This means that he pays and his insurance company will pay all costs beyond If Justin files a claim for how much will he pay, and how much will his insurance company pay?
He will pay ?750. His insurance company will pay ?1350.
Home insurance Pam and Armando’s home insurance has a deductible per incident. This means that they pay and their insurance company will pay all costs beyond If Pam and Armando file a claim for how much will they pay, and how much will their insurance company pay?
Writing Exercises
Explain why “the sum of x and y” is the same as “the sum of y and x,” but “the difference of x and y” is not the same as “the difference of y and x.” Try substituting two random numbers for and to help you explain.
Explain the difference between times the sum of and and “the sum of times and
Self Check
ⓐ After completing the exercises, use this checklist to evaluate your mastery of the objectives of this section.
ⓑ After reviewing this checklist, what will you do to become confident for all objectives?
Glossary
 term
 A term is a constant or the product of a constant and one or more variables.
 coefficient
 The constant that multiplies the variable(s) in a term is called the coefficient.
 like terms
 Terms that are either constants or have the same variables with the same exponents are like terms.
 evaluate
 To evaluate an algebraic expression means to find the value of the expression when the variable is replaced by a given number.