| 3 | X | − | 120 | ÷ | 2 | × | X | − | 120 | = | 9 | ÷ | 5 |
| 方程左边 = | 3 | X | − | 60 | X | − | 120 |
| = | - | 57 | X | − | 120 |
| - | 57 | X | − | 120 | = | 9 | ÷ | 5 |
| 方程右边 = | 9 5 |
| - | 57 | X | − | 120 | = | 9 5 |
| - | 57 | X | = | 9 5 | + | 120 |
| - | 57 | X | = | 609 5 |
| - | 609 5 | = | 57 | X |
| 57 | X | = | - | 609 5 |
| X | = | - | 609 5 | ÷ | 57 |
| = | - | 609 5 | × | 1 57 |
| = | - | 203 5 | × | 1 19 |
| X | = | - | 203 95 |
| X | = | - 2.136842 |