| 2 | a | ÷ | 7 | − | ( | 1 | − | 2 | a | ÷ | 7 | ) | ÷ | 3 | = | ( | 2 | a | ÷ | 7 | + | a | ) | ÷ | 6 |
| 方程左边 = | 2 7 | a | − | ( | 1 | − | 2 | a | ÷ | 7 | ) | × | 1 3 |
2 7 | a | − | ( | 1 | − | 2 | a | ÷ | 7 | ) | × | 1 3 | = | ( | 2 | a | ÷ | 7 | + | a | ) | ÷ | 6 |
| 方程左边 = | 2 7 | a | − | 1 | × | 1 3 | + | 2 | a | ÷ | 7 | × | 1 3 |
| = | 2 7 | a | − | 1 3 | + | 2 21 | a |
| = | 8 21 | a | − | 1 3 |
8 21 | a | − | 1 3 | = | ( | 2 | a | ÷ | 7 | + | a | ) | ÷ | 6 |
| 方程右边 = | 2 | a | ÷ | 7 | × | 1 6 | + | a | × | 1 6 |
| = | 1 21 | a | + | a | × | 1 6 |
| = | 3 14 | a |
8 21 | a | − | 1 3 | = | 3 14 | a |
8 21 | a | − | 3 14 | a | = | 1 3 |
1 6 | a | = | 1 3 |
| a | = | 1 3 | ÷ | 1 6 |
| = | 1 3 | × | 6 |
| = | 1 | × | 2 |
| a | = | 2 |