Chapter 2 - Solving Equations - 2-2 Solving Two-Step Equations - Practice and Problem-Solving Exercises - Page 92: 51

The student subtracted by 4 in the first step instead of adding. The question done correctly is below.

We need to get the x alone, so we cancel out the subtraction by adding 4 on both sides. This leaves us with the equation 2x=12. We use division to cancel out multiplication, so we divide both sides by 2 to get that x=6.