| 12000 | ( | X | − | 165 | − | 250 | ) | − | 15000000 | = | 0 |
| 方程左边 = | 12000 | X | − | 12000 | × | 165 | − | 12000 | × | 250 | − | 15000000 |
| = | 12000 | X | − | 1980000 | − | 3000000 | − | 15000000 |
| = | 12000 | X | − | 19980000 |
| 12000 | X | − | 19980000 | = | 0 |
| 12000 | X | = | 0 | + | 19980000 |
| 12000 | X | = | 19980000 |
| X | = | 19980000 | ÷ | 12000 |
| = | 19980000 | × | 1 12000 |
| = | 1665 | × | 1 |
| X | = | 1665 |