| - | 71810 | + | 60000 | + | X | − | ( | 20000 | − | 6800 | + | X | ) | X | × | 10 100 | ÷ | 4 | − | 6300 | = | 3000 |
| 方程左边 = | - | 71810 | + | 60000 | + | X | − | ( | 20000 | − | 6800 | + | X | ) | X | × | 1 40 | − | 6300 |
| = | - | 18110 | + | X | − | ( | 20000 | − | 6800 | + | X | ) | X | × | 1 40 |
| - | 18110 | + | X | − | ( | 20000 | − | 6800 | + | X | ) | X | × | 1 40 | = | 3000 |
| 方程左边 = | - | 18110 | + | X | − | 20000 | X | × | 1 40 | + | 6800 | X | × | 1 40 | − | X | X | × | 1 40 |
| = | - | 18110 | + | X | − | 500 | X | + | 170 | X | − | X | X | × | 1 40 |
| = | - | 18110 | − | 329 | X | − | X | X | × | 1 40 |
| - | 18110 | − | 329 | X | − | X | X | × | 1 40 | = | 3000 |