| ( | 180 | + | 10 | x | ) | ( | 52 | − | x | − | 40 | ) | = | 2000 |
| 方程左边 = | 180 | ( | 52 | − | x | − | 40 | ) | + | 10 | x | ( | 52 | − | x | − | 40 | ) |
| = | 180 | × | 52 | − | 180 | x | − | 180 | × | 40 | + | 10 | x | ( | 52 | − | x | − | 40 | ) |
| = | 9360 | − | 180 | x | − | 7200 | + | 10 | x | ( | 52 | − | x | − | 40 | ) |
| = | 2160 | − | 180 | x | + | 10 | x | ( | 52 | − | x | − | 40 | ) |
| = | 2160 | − | 180 | x | + | 10 | x | × | 52 | − | 10 | x | x | − | 10 | x | × | 40 |
| = | 2160 | − | 180 | x | + | 520 | x | − | 10 | x | x | − | 400 | x |
| = | 2160 | − | 60 | x | − | 10 | x | x |
| 2160 | − | 60 | x | − | 10 | x | x | = | 2000 |