| ( | x | − | 80 | ) | × | 120 | ÷ | 5 | = | ( | x | − | 80 | − | 20 | ) | × | 120 | ÷ | 10 |
| 方程左边 = | ( | x | − | 80 | ) | × | 24 |
| ( | x | − | 80 | ) | × | 24 | = | ( | x | − | 80 | − | 20 | ) | × | 120 | ÷ | 10 |
| 方程左边 = | x | × | 24 | − | 80 | × | 24 |
| = | x | × | 24 | − | 1920 |
| 24 | x | − | 1920 | = | ( | x | − | 80 | − | 20 | ) | × | 120 | ÷ | 10 |
| 方程右边 = | ( | x | − | 80 | − | 20 | ) | × | 12 |
| 24 | x | − | 1920 | = | ( | x | − | 80 | − | 20 | ) | × | 12 |
| 方程右边 = | x | × | 12 | − | 80 | × | 12 | − | 20 | × | 12 |
| = | x | × | 12 | − | 960 | − | 240 |
| = | 12 | x | − | 1200 |
| 24 | x | − | 1920 | = | 12 | x | − | 1200 |
| 24 | x | − | 12 | x | = | - | 1200 | + | 1920 |
| 12 | x | = | - | 1200 | + | 1920 |
| 12 | x | = | 720 |
| x | = | 720 | ÷ | 12 |
| = | 720 | × | 1 12 |
| = | 60 | × | 1 |
| x | = | 60 |