| 4000 | = | 84 5 | X | + | 18 5 | ( | 400 | − | X | ) |
| 方程右边 = | 84 5 | X | + | 18 5 | × | 400 | − | 18 5 | X |
| = | 84 5 | X | + | 1440 | − | 18 5 | X |
| = | 66 5 | X | + | 1440 |
| 4000 | = | 66 5 | X | + | 1440 |
| - | 66 5 | X | = | 1440 | − | 4000 |
| - | 66 5 | X | = | - | 2560 |
| 2560 | = | 66 5 | X |
66 5 | X | = | 2560 |
| X | = | 2560 | ÷ | 66 5 |
| = | 2560 | × | 5 66 |
| = | 1280 | × | 5 33 |
| X | = | 6400 33 |
| X | = | 193.939394 |