| 36 | − | ( | 6 | − | a | ) | × | 6 | ÷ | 2 | = | ( | 6 | + | a | ) | × | 6 | ÷ | 2 |
| 方程左边 = | 36 | − | ( | 6 | − | a | ) | × | 3 |
| 36 | − | ( | 6 | − | a | ) | × | 3 | = | ( | 6 | + | a | ) | × | 6 | ÷ | 2 |
| 方程左边 = | 36 | − | 6 | × | 3 | + | a | × | 3 |
| = | 36 | − | 18 | + | a | × | 3 |
| = | 18 | + | 3 | a |
| 18 | + | 3 | a | = | ( | 6 | + | a | ) | × | 6 | ÷ | 2 |
| 方程右边 = | ( | 6 | + | a | ) | × | 3 |
| 18 | + | 3 | a | = | ( | 6 | + | a | ) | × | 3 |
| 方程右边 = | 6 | × | 3 | + | a | × | 3 |
| = | 18 | + | a | × | 3 |
| 18 | + | 3 | a | = | 18 | + | 3 | a |
| 3 | a | − | 3 | a | = | 18 | − | 18 |
| 0 | a | = | 18 | − | 18 |
| 0 | a | = | 0 |