| 5000 | + | ( | x | − | 30 | ) | × | 100 | = | 7000 | + | ( | x | − | 50 | ) | × | 100 |
| 方程左边 = | 5000 | + | x | × | 100 | − | 30 | × | 100 |
| = | 5000 | + | x | × | 100 | − | 3000 |
| = | 2000 | + | 100 | x |
| 2000 | + | 100 | x | = | 7000 | + | ( | x | − | 50 | ) | × | 100 |
| 方程右边 = | 7000 | + | x | × | 100 | − | 50 | × | 100 |
| = | 7000 | + | x | × | 100 | − | 5000 |
| = | 2000 | + | 100 | x |
| 2000 | + | 100 | x | = | 2000 | + | 100 | x |
| 100 | x | − | 100 | x | = | 2000 | − | 2000 |
| 0 | x | = | 2000 | − | 2000 |
| 0 | x | = | 0 |