| ( | X | − | 860 | ) | × | 75 100 | ÷ | 3000 | = | 0 |
| 方程左边 = | ( | X | − | 860 | ) | × | 1 4000 |
| ( | X | − | 860 | ) | × | 1 4000 | = | 0 |
| 方程左边 = | X | × | 1 4000 | − | 860 | × | 1 4000 |
| = | X | × | 1 4000 | − | 43 200 |
1 4000 | X | − | 43 200 | = | 0 |
1 4000 | X | = | 0 | + | 43 200 |
1 4000 | X | = | 43 200 |
| X | = | 43 200 | ÷ | 1 4000 |
| = | 43 200 | × | 4000 |
| = | 43 | × | 20 |
| X | = | 860 |