| 30 | ( | 1 | − | y | ) | + | 60 | y | = | 25 | ( | 1 | − | y | ) | + | 75 | y |
| 方程左边 = | 30 | × | 1 | − | 30 | y | + | 60 | y |
| = | 30 | − | 30 | y | + | 60 | y |
| = | 30 | + | 30 | y |
| 30 | + | 30 | y | = | 25 | ( | 1 | − | y | ) | + | 75 | y |
| 方程右边 = | 25 | × | 1 | − | 25 | y | + | 75 | y |
| = | 25 | − | 25 | y | + | 75 | y |
| = | 25 | + | 50 | y |
| 30 | + | 30 | y | = | 25 | + | 50 | y |
| 30 | y | − | 50 | y | = | 25 | − | 30 |
| - | 20 | y | = | 25 | − | 30 |
| - | 20 | y | = | - | 5 |
| 5 | = | 20 | y |
| 20 | y | = | 5 |
| y | = | 5 | ÷ | 20 |
| = | 5 | × | 1 20 |
| = | 1 | × | 1 4 |
| y | = | 1 4 |
| y | = | 0.25 |