| 3 | ( | x | − | 7 | ) | = | 2 | ( | 1 | + | x | ) | − | 12 |
| Left side of the equation = | 3 | x | − | 3 | × | 7 |
| = | 3 | x | − | 21 |
| 3 | x | − | 21 | = | 2 | ( | 1 | + | x | ) | − | 12 |
| Right side of the equation = | 2 | × | 1 | + | 2 | x | − | 12 |
| = | 2 | + | 2 | x | − | 12 |
| = | - | 10 | + | 2 | x |
| 3 | x | − | 21 | = | - | 10 | + | 2 | x |
| 3 | x | − | 2 | x | = | - | 10 | + | 21 |
| x | = | - | 10 | + | 21 |
| x | = | - | 10 | + | 21 |
| x | = | 11 |