| ( | 40 | − | 30 | − | x | ) | ( | 600 | + | 5 | x | ) | = | 8625 |
| 方程左边 = | 40 | ( | 600 | + | 5 | x | ) | − | 30 | ( | 600 | + | 5 | x | ) | − | x | ( | 600 | + | 5 | x | ) |
| = | 40 | × | 600 | + | 40 | × | 5 | x | − | 30 | ( | 600 | + | 5 | x | ) | − | x | ( | 600 | + | 5 | x | ) |
| = | 24000 | + | 200 | x | − | 30 | ( | 600 | + | 5 | x | ) | − | x | ( | 600 | + | 5 | x | ) |
| = | 24000 | + | 200 | x | − | 30 | × | 600 | − | 30 | × | 5 | x | − | x | ( | 600 | + | 5 | x | ) |
| = | 24000 | + | 200 | x | − | 18000 | − | 150 | x | − | x | ( | 600 | + | 5 | x | ) |
| = | 6000 | + | 50 | x | − | x | ( | 600 | + | 5 | x | ) |
| = | 6000 | + | 50 | x | − | x | × | 600 | − | x | × | 5 | x |
| = | 6000 | − | 550 | x | − | x | × | 5 | x |
| 6000 | − | 550 | x | − | x | × | 5 | x | = | 8625 |