| 18 | − | x | = | ( | 60 | − | 4 | ( | 18 | − | x | ) | ) |
| Right side of the equation = | 60 | − | 4 | ( | 18 | − | x | ) |
| = | 60 | − | 4 | × | 18 | + | 4 | x |
| = | 60 | − | 72 | + | 4 | x |
| = | - | 12 | + | 4 | x |
| 18 | − | x | = | - | 12 | + | 4 | x |
| - | x | − | 4 | x | = | - | 12 | − | 18 |
| - | 5 | x | = | - | 12 | − | 18 |
| - | 5 | x | = | - | 30 |
| 30 | = | 5 | x |
| 5 | x | = | 30 |
| x | = | 30 | ÷ | 5 |
| = | 30 | × | 1 5 |
| = | 6 | × | 1 |
| x | = | 6 |