| ( | 100 | − | 18 | x | ) | ( | 8 5 | x | + | 5 2 | ) | = | 727 4 |
| 方程左边 = | 100 | ( | 8 5 | x | + | 5 2 | ) | − | 18 | x | ( | 8 5 | x | + | 5 2 | ) |
| = | 100 | × | 8 5 | x | + | 100 | × | 5 2 | − | 18 | x | ( | 8 5 | x | + | 5 2 | ) |
| = | 160 | x | + | 250 | − | 18 | x | ( | 8 5 | x | + | 5 2 | ) |
| = | 160 | x | + | 250 | − | 18 | x | × | 8 5 | x | − | 18 | x | × | 5 2 |
| = | 160 | x | + | 250 | − | 144 5 | x | x | − | 45 | x |
| = | 115 | x | + | 250 | − | 144 5 | x | x |
| 115 | x | + | 250 | − | 144 5 | x | x | = | 727 4 |