| 20 | × | 30 | − | 30 | × | 2 | x | × | 2 | − | 20 | x | × | 2 | = | 19 | ÷ | 75 | × | 30 | × | 20 |
| 方程左边 = | 600 | − | 120 | x | − | 40 | x |
| = | 600 | − | 160 | x |
| 600 | − | 160 | x | = | 19 | ÷ | 75 | × | 30 | × | 20 |
| 方程右边 = | 152 |
| 600 | − | 160 | x | = | 152 |
| - | 160 | x | = | 152 | − | 600 |
| - | 160 | x | = | - | 448 |
| 448 | = | 160 | x |
| 160 | x | = | 448 |
| x | = | 448 | ÷ | 160 |
| = | 448 | × | 1 160 |
| = | 14 | × | 1 5 |
| x | = | 14 5 |
| x | = | 2.8 |