| 90 | − | x | = | 1 | ÷ | 3 | × | ( | 180 | − | x | ) | + | 6 |
| 方程右边 = | 1 3 | ( | 180 | − | x | ) | + | 6 |
| 90 | − | x | = | 1 3 | ( | 180 | − | x | ) | + | 6 |
| 方程右边 = | 1 3 | × | 180 | − | 1 3 | x | + | 6 |
| = | 60 | − | 1 3 | x | + | 6 |
| = | 66 | − | 1 3 | x |
| 90 | − | x | = | 66 | − | 1 3 | x |
| - | x | + | 1 3 | x | = | 66 | − | 90 |
| - | 2 3 | x | = | 66 | − | 90 |
| - | 2 3 | x | = | - | 24 |
| 24 | = | 2 3 | x |
2 3 | x | = | 24 |
| x | = | 24 | ÷ | 2 3 |
| = | 24 | × | 3 2 |
| = | 12 | × | 3 |
| x | = | 36 |