Page 28 - Math Course 2 (Book 1)

Two-Step Equations

Mo. 1

Lesson 6
Let’s Begin

KEY CONCEPTS:
1. Solve two-step equations.
Solve Two-Step Equations

MO. 1 - L6a Examples

Solve Two-Step Equations Solve 3x – 4 = 17. Check your solution.

3x – 4 = 17 Write the equation.
Vocabulary A-Z 3x – 4 + 4 = 17 + 4 Undo subtraction. Add 4

Let us learn some vocabulary to each side.
3x = 21 Simplify.
3x 21
= Undo multiplication.
3 3
Divide each side by 3.
Two-step equation
x = 7 Simplify.
contains two operations. To solve two-step Check
equations, use inverse operations to undo each
operation in reverse order. 3x – 4 = 17 Write the equation.

3(7) – 4 = 17 Check to see whether this
2x + 1 = 9 sentence is true.
Two steps are needed to undo 2 operations
Step 1 First, undo addition. 17 = 17 The sentence is true.

2x + 1 = 9
Answer The solution is 7.
2x + 1 –1 = 9 –1 Subtract 1 from each side
2x = 8
Step 2 Then, undo multiplication.
n
2x = 8 Solve 3 = + 8. Check your solution.
2x 8 3
= Divide each side by 2.
2 2 3 = n +8 Write the equation.
x = 4 3
The solution is 4. n Undo addition. Subtract 8 from
3 –8 = + 8 –8
3 each side.
n
–5 = Simplify.
3
Undo division.
n
3(–5) = 3 ( ) Multiply each side by 3.
3
–15 = n Simplify.

The solution is –15.
Answer Check your solution.

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