| ( | 140 | − | m | ) | ( | 20 | + | 10 | m | ÷ | 5 | ) | = | 1250 |
| 方程左边 = | 140 | ( | 20 | + | 10 | m | ÷ | 5 | ) | − | m | ( | 20 | + | 10 | m | ÷ | 5 | ) |
| = | 140 | × | 20 | + | 140 | × | 10 | m | ÷ | 5 | − | m | ( | 20 | + | 10 | m | ÷ | 5 | ) |
| = | 2800 | + | 280 | m | − | m | ( | 20 | + | 10 | m | ÷ | 5 | ) |
| = | 2800 | + | 280 | m | − | m | × | 20 | − | m | × | 10 | m | ÷ | 5 |
| = | 2800 | + | 280 | m | − | m | × | 20 | − | m | × | 2 | m |
| = | 2800 | + | 260 | m | − | m | × | 2 | m |
| 2800 | + | 260 | m | − | m | × | 2 | m | = | 1250 |