| ( | 15 | − | 3 | ) | ( | x | − | 3 | ) | = | 60 |
| Left side of the equation = | 15 | ( | x | − | 3 | ) | − | 3 | ( | x | − | 3 | ) |
| = | 15 | x | − | 15 | × | 3 | − | 3 | ( | x | − | 3 | ) |
| = | 15 | x | − | 45 | − | 3 | ( | x | − | 3 | ) |
| = | 15 | x | − | 45 | − | 3 | x | + | 3 | × | 3 |
| = | 15 | x | − | 45 | − | 3 | x | + | 9 |
| = | 12 | x | − | 36 |
| 12 | x | − | 36 | = | 60 |
| 12 | x | = | 60 | + | 36 |
| 12 | x | = | 96 |
| x | = | 96 | ÷ | 12 |
| = | 96 | × | 1 12 |
| = | 8 | × | 1 |
| x | = | 8 |