| ( | 500 | − | a | ) | ( | 10 | + | a | ÷ | 25 | ) | = | 5400 |
| 方程左边 = | 500 | ( | 10 | + | a | ÷ | 25 | ) | − | a | ( | 10 | + | a | ÷ | 25 | ) |
| = | 500 | × | 10 | + | 500 | a | ÷ | 25 | − | a | ( | 10 | + | a | ÷ | 25 | ) |
| = | 5000 | + | 20 | a | − | a | ( | 10 | + | a | ÷ | 25 | ) |
| = | 5000 | + | 20 | a | − | a | × | 10 | − | a | a | ÷ | 25 |
| = | 5000 | + | 10 | a | − | a | a | × | 1 25 |
| 5000 | + | 10 | a | − | a | a | × | 1 25 | = | 5400 |