| 50 | × | 2 | − | x | = | ( | 20 | × | 2 | + | x | ) | × | 9 5 |
| 方程左边 = | 100 | − | x |
| 100 | − | x | = | ( | 20 | × | 2 | + | x | ) | × | 9 5 |
| 方程右边 = | 20 | × | 2 | × | 9 5 | + | x | × | 9 5 |
| = | 72 | + | x | × | 9 5 |
| 100 | − | x | = | 72 | + | 9 5 | x |
| - | x | − | 9 5 | x | = | 72 | − | 100 |
| - | 14 5 | x | = | 72 | − | 100 |
| - | 14 5 | x | = | - | 28 |
| 28 | = | 14 5 | x |
14 5 | x | = | 28 |
| x | = | 28 | ÷ | 14 5 |
| = | 28 | × | 5 14 |
| = | 2 | × | 5 |
| x | = | 10 |