| ( | 10 | + | X | ) | ( | 500 | − | 1 25 | X | ) | = | 4500 |
| 方程左边 = | 10 | ( | 500 | − | 1 25 | X | ) | + | X | ( | 500 | − | 1 25 | X | ) |
| = | 10 | × | 500 | − | 10 | × | 1 25 | X | + | X | ( | 500 | − | 1 25 | X | ) |
| = | 5000 | − | 2 5 | X | + | X | ( | 500 | − | 1 25 | X | ) |
| = | 5000 | − | 2 5 | X | + | X | × | 500 | − | X | × | 1 25 | X |
| = | 5000 | + | 2498 5 | X | − | X | × | 1 25 | X |
| 5000 | + | 2498 5 | X | − | X | × | 1 25 | X | = | 4500 |