| 18 | − | x | = | ( | 60 | − | 4 | ( | 18 | − | x | ) | ) | ÷ | 4 |
| Right side of the equation = | 60 | × | 1 4 | − | 4 | ( | 18 | − | x | ) | × | 1 4 |
| = | 15 | − | 1 | ( | 18 | − | x | ) |
| = | 15 | − | 1 | × | 18 | + | 1 | x |
| = | 15 | − | 18 | + | 1 | x |
| = | - | 3 | + | 1 | x |
| 18 | − | x | = | - | 3 | + | 1 | x |
| - | x | − | 1 | x | = | - | 3 | − | 18 |
| - | 2 | x | = | - | 3 | − | 18 |
| - | 2 | x | = | - | 21 |
| 21 | = | 2 | x |
| 2 | x | = | 21 |
| x | = | 21 | ÷ | 2 |
| = | 21 | × | 1 2 |
| x | = | 21 2 |
| x | = | 10.5 |