| ( | 30 | + | 18 5 | x | ) | ( | 1 | − | 1 500 | x | ) | × | 390 | = | 35100 |
| 方程左边 = | 30 | ( | 1 | − | 1 500 | x | ) | × | 390 | + | 18 5 | x | ( | 1 | − | 1 500 | x | ) | × | 390 |
| = | 11700 | ( | 1 | − | 1 500 | x | ) | + | 1404 | x | ( | 1 | − | 1 500 | x | ) |
| = | 11700 | × | 1 | − | 11700 | × | 1 500 | x | + | 1404 | x | ( | 1 | − | 1 500 | x | ) |
| = | 11700 | − | 117 5 | x | + | 1404 | x | ( | 1 | − | 1 500 | x | ) |
| = | 11700 | − | 117 5 | x | + | 1404 | x | × | 1 | − | 1404 | x | × | 1 500 | x |
| = | 11700 | − | 117 5 | x | + | 1404 | x | − | 351 125 | x | x |
| = | 11700 | + | 6903 5 | x | − | 351 125 | x | x |
| 11700 | + | 6903 5 | x | − | 351 125 | x | x | = | 35100 |