| ( | 4 5 | y | − | 5 | ) | ÷ | ( | y | − | 10 | ) | = | 9 | ÷ | 10 |
| 方程两边同时乘以: | ( | y | − | 10 | ) |
| ( | 4 5 | y | − | 5 | ) | = | 9 | ÷ | 10 | × | ( | y | − | 10 | ) |
4 5 | y | − | 5 | = | 9 | ÷ | 10 | × | ( | y | − | 10 | ) |
4 5 | y | − | 5 | = | 9 | ÷ | 10 | × | y | − | 9 | ÷ | 10 | × | 10 |
4 5 | y | − | 5 | = | 9 10 | y | − | 9 |
4 5 | y | − | 9 10 | y | = | - | 9 | + | 5 |
| - | 1 10 | y | = | - | 9 | + | 5 |
| - | 1 10 | y | = | - | 4 |
| 4 | = | 1 10 | y |
1 10 | y | = | 4 |
| y | = | 4 | ÷ | 1 10 |
| = | 4 | × | 10 |
| y | = | 40 |