Solving Two-Step Equations

Lesson 5

Write an equation for each statement and solve to determine the unknown number.

1. The sum of a number and twenty is eighty-seven.

2. The quotient of a number and four is negative six.

3. A number decreased by three tenths is one and two tenths.

Target: Solve two-step equations.

Solve the equation for x. Check the solution.

8x – 3 = 85 + 3 + 3 8x = 88 8 8 x = 11

8(11) – 3 = 88 – 3 = 85

Solve the equation for x. Check the solution.

59

2 x

55

9)7(x

9 9

x 63

25759

63

Use an equation mat to illustrate and solve the equation 2x – 4 = 6.

Set up the mat.

Add four positive chips.

Divide into equal groups.

Solution: x = 5

Eight more than 3 times a number is 29. Write and solve an equation to find the value of the number.

3x + 8 = 29 – 8 – 8 3x = 21 3 3 x = 7

3(7) + 8 = 21 + 8 = 29

Solve each equation for x.

1. 4x + 5 = 49

2.

3. 5 – 2x = 25

83

20 x

Why is it important to show your work and check your solution when solving an equation?