| 12 | − | ( | 2 | x | − | 3 | ) | = | 3 | ( | x | + | 10 | ) |
| Left side of the equation = | 12 | − | 2 | x | + | 3 |
| = | 15 | − | 2 | x |
| 15 | − | 2 | x | = | 3 | ( | x | + | 10 | ) |
| Right side of the equation = | 3 | x | + | 3 | × | 10 |
| = | 3 | x | + | 30 |
| 15 | − | 2 | x | = | 3 | x | + | 30 |
| - | 2 | x | − | 3 | x | = | 30 | − | 15 |
| - | 5 | x | = | 30 | − | 15 |
| - | 5 | x | = | 15 |
| - | 15 | = | 5 | x |
| 5 | x | = | - | 15 |
| x | = | - | 15 | ÷ | 5 |
| = | - | 15 | × | 1 5 |
| = | - | 3 | × | 1 |
| x | = | - | 3 |