| ( | 300 | − | 33 2 | n | ) | ( | 30 | + | n | ) | = | ( | 50 | − | n | ) | ( | 180 | + | 33 2 | n | ) |
| 方程左边 = | 300 | ( | 30 | + | n | ) | − | 33 2 | n | ( | 30 | + | n | ) |
| = | 300 | × | 30 | + | 300 | n | − | 33 2 | n | ( | 30 | + | n | ) |
| = | 9000 | + | 300 | n | − | 33 2 | n | ( | 30 | + | n | ) |
| = | 9000 | + | 300 | n | − | 33 2 | n | × | 30 | − | 33 2 | n | n |
| = | 9000 | + | 300 | n | − | 495 | n | − | 33 2 | n | n |
| = | 9000 | − | 195 | n | − | 33 2 | n | n |
| 9000 | − | 195 | n | − | 33 2 | n | n | = | ( | 50 | − | n | ) | ( | 180 | + | 33 2 | n | ) |
| 方程右边 = | 50 | ( | 180 | + | 33 2 | n | ) | − | n | ( | 180 | + | 33 2 | n | ) |
| = | 50 | × | 180 | + | 50 | × | 33 2 | n | − | n | ( | 180 | + | 33 2 | n | ) |
| = | 9000 | + | 825 | n | − | n | ( | 180 | + | 33 2 | n | ) |
| = | 9000 | + | 825 | n | − | n | × | 180 | − | n | × | 33 2 | n |
| = | 9000 | + | 645 | n | − | n | × | 33 2 | n |
| 9000 | − | 195 | n | − | 33 2 | n | n | = | 9000 | + | 645 | n | − | n | × | 33 2 | n |