| 120 | + | ( | x | − | 120 | ) | x | × | 2 | ÷ | 5 | = | 1 | ÷ | 2 | × | x |
| 方程左边 = | 120 | + | ( | x | − | 120 | ) | x | × | 2 5 |
| 120 | + | ( | x | − | 120 | ) | x | × | 2 5 | = | 1 | ÷ | 2 | × | x |
| 方程左边 = | 120 | + | x | x | × | 2 5 | − | 120 | x | × | 2 5 |
| = | 120 | + | x | x | × | 2 5 | − | 48 | x |
| 120 | + | x | x | × | 2 5 | − | 48 | x | = | 1 | ÷ | 2 | × | x |
| 方程右边 = | 1 2 | x |
| 120 | + | x | x | × | 2 5 | − | 48 | x | = | 1 2 | x |