| 12 | x | + | 2 | ( | x | − | 3 | ) | − | 3 | x | = | 126 |
| Left side of the equation = | 9 | x | + | 2 | ( | x | − | 3 | ) |
| 9 | x | + | 2 | ( | x | − | 3 | ) | = | 126 |
| Left side of the equation = | 9 | x | + | 2 | x | − | 2 | × | 3 |
| = | 9 | x | + | 2 | x | − | 6 |
| = | 11 | x | − | 6 |
| 11 | x | − | 6 | = | 126 |
| 11 | x | = | 126 | + | 6 |
| 11 | x | = | 132 |
| x | = | 132 | ÷ | 11 |
| = | 132 | × | 1 11 |
| = | 12 | × | 1 |
| x | = | 12 |