| x | ( | 45 | − | x | ) | − | ( | x | + | 5 | ) | ( | 40 | − | x | ) | = | 50 |
| 方程左边 = | x | × | 45 | − | x | x | − | ( | x | + | 5 | ) | ( | 40 | − | x | ) |
| = | 45 | x | − | x | x | − | x | ( | 40 | − | x | ) | − | 5 | ( | 40 | − | x | ) |
| = | 45 | x | − | x | x | − | x | × | 40 | + | x | x | − | 5 | ( | 40 | − | x | ) |
| = | 5 | x | − | x | x | + | x | x | − | 5 | ( | 40 | − | x | ) |
| = | 5 | x | − | x | x | + | x | x | − | 5 | × | 40 | + | 5 | x |
| = | 5 | x | − | x | x | + | x | x | − | 200 | + | 5 | x |
| = | 10 | x | − | x | x | + | x | x | − | 200 |
| 10 | x | − | x | x | + | x | x | − | 200 | = | 50 |