Evaluating Expressions

Evaluating Expressions

What is an expression?

An expression in math is a math statement with numbers and/or variables, and some kind of operation between them (like adding, subtracting, multiplying, or dividing)

For example:
7 + 9
25 x 6
x + 2
ab - 2bc

Evaluating an Expression

For our purposes, when we evaluate an expression, we will be looking at expressions with variables, and replacing those variables with a number, and then solving using BEDMAS.

EXAMPLE

Evaluate 2x + 5 for x = 4

We will replace the x with 4, and then evaluate the expression:

2(4) + 5 = 8 + 5 = 13

Note: 2x means 2 times x, so if we replace it with 4,
it would be 2 times 4.

EXAMPLE 2

Evaluate 3x - 2y for x = 2 and y = -3

Replace x and y with the values, and then solve. Don't forget BEDMAS!

3(2) - 2(-3)
= 6 - (-6)
= 6 + 6 = 12

EXAMPLE 3

Evaluate 3xy - z for x = 4, y = -5 and z = 7

Replace x, y, and z with the values, and then solve. Don't forget BEDMAS!

3(4)(-5) - 7
= -60 - 7 = -67

You Try!

Try evaluating these expressions with the given values!

Multiple Choice

What is the value of 3x when x = 4

• 3

• 4

• 7

• 12

Multiple Choice

What is the value of 4x if x = -2

• -8

• -2

• 2

• 4

Multiple Choice

What is the value of 2x - 5 when x = 3

• 1

• 3

• 5

• 7

Multiple Choice

What is the value of 4x + 7 when x = -3

• -19

• -7

• -5

• 5

Multiple Choice

What is the value of 3xy if x = 4 and y = -2

• 5

• -5

• 24

• -24

Multiple Choice

What is the value of 3x - 2y if x = 3 and y = 2

• 1

• 3

• 5

• 7

Multiple Choice

What is the value of 4x + 2y if x = -3 and y = -4

• -25

• -20

• -12

• -4

Multiple Choice

What is the value of 4ab - c if a = 2, b = -3, and c = -5

• -29

• -24

• -19

• -

Multiple Choice

What is the value of -3a - 2bc if a = -2, b = 3, and c = -1

• -12
• 0
• 6

• 12

Multiple Choice

What is the value of $$-3x\ -\ \frac{y}{3}$$ if x = -5 and y = 3

• -16

• -14

• 14

• 16