| ( | 500 | − | 107 100 | X | − | 187 | ) | × | 15 | = | 2500 |
| 方程左边 = | 500 | × | 15 | − | 107 100 | X | × | 15 | − | 187 | × | 15 |
| = | 7500 | − | 321 20 | X | − | 2805 |
| = | 4695 | − | 321 20 | X |
| 4695 | − | 321 20 | X | = | 2500 |
| - | 321 20 | X | = | 2500 | − | 4695 |
| - | 321 20 | X | = | - | 2195 |
| 2195 | = | 321 20 | X |
321 20 | X | = | 2195 |
| X | = | 2195 | ÷ | 321 20 |
| = | 2195 | × | 20 321 |
| X | = | 43900 321 |
| X | = | 136.760125 |