| 2 | ( | 120 | + | x | ) | = | 6 | ( | 120 | + | x | ) |
| 方程左边 = | 2 | × | 120 | + | 2 | x |
| = | 240 | + | 2 | x |
| 240 | + | 2 | x | = | 6 | ( | 120 | + | x | ) |
| 方程右边 = | 6 | × | 120 | + | 6 | x |
| = | 720 | + | 6 | x |
| 240 | + | 2 | x | = | 720 | + | 6 | x |
| 2 | x | − | 6 | x | = | 720 | − | 240 |
| - | 4 | x | = | 720 | − | 240 |
| - | 4 | x | = | 480 |
| - | 480 | = | 4 | x |
| 4 | x | = | - | 480 |
| x | = | - | 480 | ÷ | 4 |
| = | - | 480 | × | 1 4 |
| = | - | 120 | × | 1 |
| x | = | - | 120 |