| 200 | × | 3 5 | x | + | 100 | × | 3 10 | x | + | 100 | ( | - | 3 10 | x | ) | = | 15000 |
| 方程左边 = | 120 | x | + | 30 | x | + | 100 | ( | - | 3 10 | x | ) |
| = | 150 | x | + | 100 | ( | - | 3 10 | x | ) |
| 150 | x | + | 100 | ( | - | 3 10 | x | ) | = | 15000 |
| 方程左边 = | 150 | x | − | 100 | × | 3 10 | x |
| = | 150 | x | − | 30 | x |
| = | 120 | x |
| 120 | x | = | 15000 |
| x | = | 15000 | ÷ | 120 |
| = | 15000 | × | 1 120 |
| = | 125 | × | 1 |
| x | = | 125 |