| ( | X | + | 50 100 | X | ) | × | 90 100 | + | 50 | = | X | − | 370 |
| 方程左边 = | X | × | 90 100 | + | 50 100 | X | × | 90 100 | + | 50 |
| = | X | × | 90 100 | + | 9 20 | X | + | 50 |
| = | 27 20 | X | + | 50 |
27 20 | X | + | 50 | = | X | − | 370 |
27 20 | X | − | X | = | - | 370 | − | 50 |
7 20 | X | = | - | 370 | − | 50 |
7 20 | X | = | - | 420 |
| X | = | - | 420 | ÷ | 7 20 |
| = | - | 420 | × | 20 7 |
| = | - | 60 | × | 20 |
| X | = | - | 1200 |