| 200 | x | + | ( | 170 | − | x | ) | × | 400 | = | 49200 |
| 方程左边 = | 200 | x | + | 170 | × | 400 | − | x | × | 400 |
| = | 200 | x | + | 68000 | − | x | × | 400 |
| = | - | 200 | x | + | 68000 |
| - | 200 | x | + | 68000 | = | 49200 |
| - | 200 | x | = | 49200 | − | 68000 |
| - | 200 | x | = | - | 18800 |
| 18800 | = | 200 | x |
| 200 | x | = | 18800 |
| x | = | 18800 | ÷ | 200 |
| = | 18800 | × | 1 200 |
| = | 94 | × | 1 |
| x | = | 94 |