| ( | x | − | 40 | ) | ( | 180 | + | 10 | ( | 52 | − | x | ) | ) | = | 2000 |
| 方程左边 = | x | ( | 180 | + | 10 | ( | 52 | − | x | ) | ) | − | 40 | ( | 180 | + | 10 | ( | 52 | − | x | ) | ) |
| = | x | × | 180 | + | x | × | 10 | ( | 52 | − | x | ) | − | 40 | ( | 180 | + | 10 | ( | 52 | − | x | ) | ) |
| = | 180 | x | + | x | × | 10 | × | 52 | − | x | × | 10 | x | − | 40 | ( | 180 | + | 10 | ( | 52 | − | x | ) | ) |
| = | 180 | x | + | x | × | 520 | − | x | × | 10 | x | − | 40 | ( | 180 | + | 10 | ( | 52 | − | x | ) | ) |
| = | 700 | x | − | x | × | 10 | x | − | 40 | ( | 180 | + | 10 | ( | 52 | − | x | ) | ) |
| = | 700 | x | − | x | × | 10 | x | − | 40 | × | 180 | − | 40 | × | 10 | ( | 52 | − | x | ) |
| = | 700 | x | − | x | × | 10 | x | − | 7200 | − | 400 | ( | 52 | − | x | ) |
| = | 700 | x | − | x | × | 10 | x | − | 7200 | − | 400 | × | 52 | + | 400 | x |
| = | 700 | x | − | x | × | 10 | x | − | 7200 | − | 20800 | + | 400 | x |
| = | 1100 | x | − | x | × | 10 | x | − | 28000 |
| 1100 | x | − | x | × | 10 | x | − | 28000 | = | 2000 |