7 2000 | x | + | 3 500 | ( | 4800 | − | x | ) | = | 124 5 |
| 方程左边 = | 7 2000 | x | + | 3 500 | × | 4800 | − | 3 500 | x |
| = | 7 2000 | x | + | 144 5 | − | 3 500 | x |
| = | - | 1 400 | x | + | 144 5 |
| - | 1 400 | x | + | 144 5 | = | 124 5 |
| - | 1 400 | x | = | 124 5 | − | 144 5 |
| - | 1 400 | x | = | - | 4 |
| 4 | = | 1 400 | x |
1 400 | x | = | 4 |
| x | = | 4 | ÷ | 1 400 |
| = | 4 | × | 400 |
| x | = | 1600 |