| X | × | 70 100 | + | ( | 160 | − | X | ) | × | 90 100 | = | 160 | × | 85 100 |
| 方程左边 = | 70 100 | X | + | 160 | × | 90 100 | − | X | × | 90 100 |
| = | 70 100 | X | + | 144 | − | X | × | 90 100 |
| = | - | 1 5 | X | + | 144 |
| - | 1 5 | X | + | 144 | = | 160 | × | 85 100 |
| 方程右边 = | 136 |
| - | 1 5 | X | + | 144 | = | 136 |
| - | 1 5 | X | = | 136 | − | 144 |
| - | 1 5 | X | = | - | 8 |
| 8 | = | 1 5 | X |
1 5 | X | = | 8 |
| X | = | 8 | ÷ | 1 5 |
| = | 8 | × | 5 |
| X | = | 40 |