| ( | X | − | 5000 | ) | × | 3 100 | = | X | − | 20000 |
| 方程左边 = | X | × | 3 100 | − | 5000 | × | 3 100 |
| = | X | × | 3 100 | − | 150 |
3 100 | X | − | 150 | = | X | − | 20000 |
3 100 | X | − | X | = | - | 20000 | + | 150 |
| - | 97 100 | X | = | - | 20000 | + | 150 |
| - | 97 100 | X | = | - | 19850 |
| 19850 | = | 97 100 | X |
97 100 | X | = | 19850 |
| X | = | 19850 | ÷ | 97 100 |
| = | 19850 | × | 100 97 |
| X | = | 1985000 97 |
| X | = | 20463.917526 |