| 36 | − | ( | 6 | − | a | ) | × | 6 | ÷ | 2 | = | 30 | − | 4 | a | ÷ | 2 |
| 方程左边 = | 36 | − | ( | 6 | − | a | ) | × | 3 |
| 36 | − | ( | 6 | − | a | ) | × | 3 | = | 30 | − | 4 | a | ÷ | 2 |
| 方程左边 = | 36 | − | 6 | × | 3 | + | a | × | 3 |
| = | 36 | − | 18 | + | a | × | 3 |
| = | 18 | + | 3 | a |
| 18 | + | 3 | a | = | 30 | − | 4 | a | ÷ | 2 |
| 方程右边 = | 30 | − | 2 | a |
| 18 | + | 3 | a | = | 30 | − | 2 | a |
| 3 | a | + | 2 | a | = | 30 | − | 18 |
| 5 | a | = | 30 | − | 18 |
| 5 | a | = | 12 |
| a | = | 12 | ÷ | 5 |
| = | 12 | × | 1 5 |
| a | = | 12 5 |
| a | = | 2.4 |