| ( | 6 | + | a | ) | × | 4 | ÷ | 2 | = | 14 | a | ÷ | 2 | − | 30 |
| 方程左边 = | ( | 6 | + | a | ) | × | 2 |
| ( | 6 | + | a | ) | × | 2 | = | 14 | a | ÷ | 2 | − | 30 |
| 方程左边 = | 6 | × | 2 | + | a | × | 2 |
| = | 12 | + | a | × | 2 |
| 12 | + | 2 | a | = | 14 | a | ÷ | 2 | − | 30 |
| 方程右边 = | 7 | a | − | 30 |
| 12 | + | 2 | a | = | 7 | a | − | 30 |
| 2 | a | − | 7 | a | = | - | 30 | − | 12 |
| - | 5 | a | = | - | 30 | − | 12 |
| - | 5 | a | = | - | 42 |
| 42 | = | 5 | a |
| 5 | a | = | 42 |
| a | = | 42 | ÷ | 5 |
| = | 42 | × | 1 5 |
| a | = | 42 5 |
| a | = | 8.4 |