10 100 | x | + | 30 100 | ( | 3000 | − | x | ) | = | 12 100 | × | 3000 |
| 方程左边 = | 10 100 | x | + | 30 100 | × | 3000 | − | 30 100 | x |
| = | 10 100 | x | + | 900 | − | 30 100 | x |
| = | - | 1 5 | x | + | 900 |
| - | 1 5 | x | + | 900 | = | 12 100 | × | 3000 |
| 方程右边 = | 360 |
| - | 1 5 | x | + | 900 | = | 360 |
| - | 1 5 | x | = | 360 | − | 900 |
| - | 1 5 | x | = | - | 540 |
| 540 | = | 1 5 | x |
1 5 | x | = | 540 |
| x | = | 540 | ÷ | 1 5 |
| = | 540 | × | 5 |
| x | = | 2700 |