1. Solving Two-Step Equations
Lesson 20
Introductory Algebra
Solving Two-Step Equations

2. Warm-Up Solve each equation. Show all work and check your solution.
100 = x + 76
15a = 60
k – 0.84 = 1.1
The base of a triangle is 4 feet. The area of the triangle is 9 square feet. What is the height of the triangle?
The area of a rectangle is 400 square feet. Its width is 8 feet. What is the length of the rectangle?

3. Solving Two-Step Equations
Target:
Solve two-step equations.

4. Vocabulary
Two-step Equation: An equation with two different operations.

6. Example 1 Solve each equation. Check the solution. 7x – 3 = 74 +3 +3
7x = 77
x = 11
7(11) – 3 = 74
77 – 3 = 74

7. Example 2a
Write an equation for the statement. Solve the problem and check the solution. Three times a number x increased by 8 is 29. 3x + 8 = 29 – 8 – 8 3x = x = 7 3(7) + 8 = = 29

8. Example 2b Write an equation for the statement. Solve the problem and
check the solution.
Twice a number x minus 7 is 5.
2x – 7 = 5
2x = 12
x = 6
2(6) – 7 = 12 – 7 = 5

9. Example 3 John and Erin shared a bag of chocolate candies. John ate
five fewer than three times as many candies as Erin ate.
If John ate 43 candies, how many candies did Erin eat?
Equation: 3c – 5 = 43
3c = 48
c = 16
Erin ate 16 candies.

10. Exit Problems Solve for x. Check your solution. 3x + 1 = 19

11. Communication Prompt
What do you think are the most common mistakes students make when solving equations? Why do you think that?