| 3000 | = | ( | 10 | + | X | ) | X | ( | 200 | − | 5 | X | ) |
| 方程右边 = | 10 | X | ( | 200 | − | 5 | X | ) | + | X | X | ( | 200 | − | 5 | X | ) |
| = | 10 | X | × | 200 | − | 10 | X | × | 5 | X | + | X | X | ( | 200 | − | 5 | X | ) |
| = | 2000 | X | − | 50 | X | X | + | X | X | ( | 200 | − | 5 | X | ) |
| = | 2000 | X | − | 50 | X | X | + | X | X | × | 200 | − | X | X | × | 5 | X |
| 3000 | = | 2000 | X | − | 50 | X | X | + | X | X | × | 200 | − | X | X | × | 5 | X |