| ( | 1000 | − | 600 | − | X | ) | ( | 1 | − | 25 100 | ) | = | 180 |
| 方程左边 = | 1000 | ( | 1 | − | 25 100 | ) | − | 600 | ( | 1 | − | 25 100 | ) | − | X | ( | 1 | − | 25 100 | ) |
| = | 1000 | × | 1 | − | 1000 | × | 25 100 | − | 600 | ( | 1 | − | 25 100 | ) | − | X | ( | 1 | − | 25 100 | ) |
| = | 1000 | − | 250 | − | 600 | ( | 1 | − | 25 100 | ) | − | X | ( | 1 | − | 25 100 | ) |
| = | 750 | − | 600 | ( | 1 | − | 25 100 | ) | − | X | ( | 1 | − | 25 100 | ) |
| = | 750 | − | 600 | × | 1 | + | 600 | × | 25 100 | − | X | ( | 1 | − | 25 100 | ) |
| = | 750 | − | 600 | + | 150 | − | X | ( | 1 | − | 25 100 | ) |
| = | 300 | − | X | ( | 1 | − | 25 100 | ) |
| = | 300 | − | X | × | 1 | + | X | × | 25 100 |
| = | 300 | − | 3 4 | X |
| 300 | − | 3 4 | X | = | 180 |
| - | 3 4 | X | = | 180 | − | 300 |
| - | 3 4 | X | = | - | 120 |
| 120 | = | 3 4 | X |
3 4 | X | = | 120 |
| X | = | 120 | ÷ | 3 4 |
| = | 120 | × | 4 3 |
| = | 40 | × | 4 |
| X | = | 160 |