| ( | 20 | − | 2 | X | ) | ( | 50 | − | 3 | X | ) | = | 1000 | × | 3 | ÷ | 4 |
| 方程左边 = | 20 | ( | 50 | − | 3 | X | ) | − | 2 | X | ( | 50 | − | 3 | X | ) |
| = | 20 | × | 50 | − | 20 | × | 3 | X | − | 2 | X | ( | 50 | − | 3 | X | ) |
| = | 1000 | − | 60 | X | − | 2 | X | ( | 50 | − | 3 | X | ) |
| = | 1000 | − | 60 | X | − | 2 | X | × | 50 | + | 2 | X | × | 3 | X |
| = | 1000 | − | 60 | X | − | 100 | X | + | 6 | X | X |
| = | 1000 | − | 160 | X | + | 6 | X | X |
| 1000 | − | 160 | X | + | 6 | X | X | = | 1000 | × | 3 | ÷ | 4 |
| 方程右边 = | 750 |
| 1000 | − | 160 | X | + | 6 | X | X | = | 750 |
| X1= | 5 3 |
| X2=25 |