| ( | 30 | − | 2 | x | ) | ( | 40 | − | 2 | x | ÷ | 2 | ) | = | 950 |
| 方程左边 = | 30 | ( | 40 | − | 2 | x | ÷ | 2 | ) | − | 2 | x | ( | 40 | − | 2 | x | ÷ | 2 | ) |
| = | 30 | × | 40 | − | 30 | × | 2 | x | ÷ | 2 | − | 2 | x | ( | 40 | − | 2 | x | ÷ | 2 | ) |
| = | 1200 | − | 30 | x | − | 2 | x | ( | 40 | − | 2 | x | ÷ | 2 | ) |
| = | 1200 | − | 30 | x | − | 2 | x | × | 40 | + | 2 | x | × | 2 | x | ÷ | 2 |
| = | 1200 | − | 30 | x | − | 80 | x | + | 2 | x | x |
| = | 1200 | − | 110 | x | + | 2 | x | x |
| 1200 | − | 110 | x | + | 2 | x | x | = | 950 |