| ( | 1 | − | 5 | m | ) | ÷ | ( | 4 | ÷ | 5 | × | m | ) | = | - | 1 |
| 方程两边同时乘以: | ( | 4 | ÷ | 5 | × | m | ) |
| ( | 1 | − | 5 | m | ) | = | - | 1 | ( | 4 | ÷ | 5 | × | m | ) |
| 1 | − | 5 | m | = | - | 1 | ( | 4 | ÷ | 5 | × | m | ) |
| 1 | − | 5 | m | = | - | 1 | × | 4 | ÷ | 5 | × | m |
| 1 | − | 5 | m | = | - | 4 5 | m |
| - | 5 | m | + | 4 5 | m | = | - | 1 |
| - | 21 5 | m | = | - | 1 |
| 1 | = | 21 5 | m |
21 5 | m | = | 1 |
| m | = | 1 | ÷ | 21 5 |
| = | 1 | × | 5 21 |
| m | = | 5 21 |
| m | = | 0.238095 |