| 6000 | = | ( | X | + | 10 | ) | ( | 500 | − | 20 | X | ) |
| 方程右边 = | X | ( | 500 | − | 20 | X | ) | + | 10 | ( | 500 | − | 20 | X | ) |
| = | X | × | 500 | − | X | × | 20 | X | + | 10 | ( | 500 | − | 20 | X | ) |
| = | 500 | X | − | X | × | 20 | X | + | 10 | × | 500 | − | 10 | × | 20 | X |
| = | 500 | X | − | X | × | 20 | X | + | 5000 | − | 200 | X |
| = | 300 | X | − | X | × | 20 | X | + | 5000 |
| 6000 | = | 300 | X | − | X | × | 20 | X | + | 5000 |