| ( | ( | Y | + | 10 | ) | ÷ | 5 | ) | − | ( | Y | − | 10 | ) | = | 0 |
| 方程左边 = | ( | Y | + | 10 | ) | ÷ | 5 | − | ( | Y | − | 10 | ) |
| = | Y | × | 1 5 | + | 10 | × | 1 5 | − | ( | Y | − | 10 | ) |
| = | Y | × | 1 5 | + | 2 | − | ( | Y | − | 10 | ) |
| = | 1 5 | Y | + | 2 | − | Y | + | 10 |
| = | - | 4 5 | Y | + | 12 |
| - | 4 5 | Y | + | 12 | = | 0 |
| - | 4 5 | Y | = | 0 | − | 12 |
| - | 4 5 | Y | = | - | 12 |
| 12 | = | 4 5 | Y |
4 5 | Y | = | 12 |
| Y | = | 12 | ÷ | 4 5 |
| = | 12 | × | 5 4 |
| = | 3 | × | 5 |
| Y | = | 15 |