| ( | X | − | 80 | ) | ( | 1 | − | 25 100 | ) | ÷ | 4200 | = | ( | X | − | 160 | ) | ( | 1 | − | 25 100 | ) | ÷ | 4000 |
| 方程左边 = | X | ( | 1 | − | 25 100 | ) | × | 1 4200 | − | 80 | ( | 1 | − | 25 100 | ) | × | 1 4200 |
| = | X | ( | 1 | − | 25 100 | ) | × | 1 4200 | − | 2 105 | ( | 1 | − | 25 100 | ) |
| = | X | × | 1 | × | 1 4200 | − | X | × | 25 100 | × | 1 4200 | − | 2 105 | ( | 1 | − | 25 100 | ) |
| = | X | × | 1 4200 | − | X | × | 1 16800 | − | 2 105 | ( | 1 | − | 25 100 | ) |
| = | 1 5600 | X | − | 2 105 | ( | 1 | − | 25 100 | ) |
| = | 1 5600 | X | − | 2 105 | × | 1 | + | 2 105 | × | 25 100 |
| = | 1 5600 | X | − | 2 105 | + | 1 210 |
| = | 1 5600 | X | − | 1 70 |
1 5600 | X | − | 1 70 | = | ( | X | − | 160 | ) | ( | 1 | − | 25 100 | ) | ÷ | 4000 |
| 方程右边 = | X | ( | 1 | − | 25 100 | ) | × | 1 4000 | − | 160 | ( | 1 | − | 25 100 | ) | × | 1 4000 |
| = | X | ( | 1 | − | 25 100 | ) | × | 1 4000 | − | 1 25 | ( | 1 | − | 25 100 | ) |
| = | X | × | 1 | × | 1 4000 | − | X | × | 25 100 | × | 1 4000 | − | 1 25 | ( | 1 | − | 25 100 | ) |
| = | X | × | 1 4000 | − | X | × | 1 16000 | − | 1 25 | ( | 1 | − | 25 100 | ) |
| = | 3 16000 | X | − | 1 25 | ( | 1 | − | 25 100 | ) |
| = | 3 16000 | X | − | 1 25 | × | 1 | + | 1 25 | × | 25 100 |
| = | 3 16000 | X | − | 1 25 | + | 1 100 |
| = | 3 16000 | X | − | 3 100 |
1 5600 | X | − | 1 70 | = | 3 16000 | X | − | 3 100 |
1 5600 | X | − | 3 16000 | X | = | - | 3 100 | + | 1 70 |
| - | 1 112000 | X | = | - | 3 100 | + | 1 70 |
| - | 1 112000 | X | = | - | 11 700 |
11 700 | = | 1 112000 | X |
1 112000 | X | = | 11 700 |
| X | = | 11 700 | ÷ | 1 112000 |
| = | 11 700 | × | 112000 |
| = | 11 | × | 160 |
| X | = | 1760 |