| 5 | ( | y | + | 8 | ) | − | 5 | = | 4 | ( | 2 | y | − | 7 | ) |
| 方程左边 = | 5 | y | + | 5 | × | 8 | − | 5 |
| = | 5 | y | + | 40 | − | 5 |
| = | 5 | y | + | 35 |
| 5 | y | + | 35 | = | 4 | ( | 2 | y | − | 7 | ) |
| 方程右边 = | 4 | × | 2 | y | − | 4 | × | 7 |
| = | 8 | y | − | 28 |
| 5 | y | + | 35 | = | 8 | y | − | 28 |
| 5 | y | − | 8 | y | = | - | 28 | − | 35 |
| - | 3 | y | = | - | 28 | − | 35 |
| - | 3 | y | = | - | 63 |
| 63 | = | 3 | y |
| 3 | y | = | 63 |
| y | = | 63 | ÷ | 3 |
| = | 63 | × | 1 3 |
| = | 21 | × | 1 |
| y | = | 21 |