Question

Tobin is solving the equation 3(x - 1.25) = 11.25. His work is shown below.

3(x - 1.25) = 11.25
3x - 3.75 = 11.25
3x - 3.75 + 3.75 = 11.25 + 3.75
3x = 15
3x • 3 = 45.3
x = 135
What mistake did Tobin make?

Answer 1

Instead of dividing by 3, he multiplied by 3

Explanation:

3x = 15

Divide both sides by 3

3x/3 = 15/3

x= 5