| 160 | x | + | ( | 30 | − | x | ) | ( | 2 | × | 160 | − | 80 | ) | = | 5600 |
| 方程左边 = | 160 | x | + | 30 | ( | 2 | × | 160 | − | 80 | ) | − | x | ( | 2 | × | 160 | − | 80 | ) |
| = | 160 | x | + | 30 | × | 2 | × | 160 | − | 30 | × | 80 | − | x | ( | 2 | × | 160 | − | 80 | ) |
| = | 160 | x | + | 9600 | − | 2400 | − | x | ( | 2 | × | 160 | − | 80 | ) |
| = | 160 | x | + | 7200 | − | x | ( | 2 | × | 160 | − | 80 | ) |
| = | 160 | x | + | 7200 | − | x | × | 2 | × | 160 | + | x | × | 80 |
| = | 160 | x | + | 7200 | − | x | × | 320 | + | x | × | 80 |
| = | - | 80 | x | + | 7200 |
| - | 80 | x | + | 7200 | = | 5600 |
| - | 80 | x | = | 5600 | − | 7200 |
| - | 80 | x | = | - | 1600 |
| 1600 | = | 80 | x |
| 80 | x | = | 1600 |
| x | = | 1600 | ÷ | 80 |
| = | 1600 | × | 1 80 |
| = | 20 | × | 1 |
| x | = | 20 |