| ( | 513 500 | − | X | ) | ÷ | 513 500 | = | 15 100 |
| 方程左边 = | 513 500 | × | 500 513 | − | X | × | 500 513 |
| = | 1 | − | X | × | 500 513 |
| 1 | − | 500 513 | X | = | 15 100 |
| - | 500 513 | X | = | 15 100 | − | 1 |
| - | 500 513 | X | = | - | 17 20 |
17 20 | = | 500 513 | X |
500 513 | X | = | 17 20 |
| X | = | 17 20 | ÷ | 500 513 |
| = | 17 20 | × | 513 500 |
| X | = | 8721 10000 |
| X | = | 0.8721 |