| ( | a | + | 3 | ) | ÷ | 4 | − | ( | 2 | a | − | 3 | ) | ÷ | 7 | = | 1 |
| 方程左边 = | a | × | 1 4 | + | 3 | × | 1 4 | − | ( | 2 | a | − | 3 | ) | × | 1 7 |
| = | a | × | 1 4 | + | 3 4 | − | ( | 2 | a | − | 3 | ) | × | 1 7 |
| = | 1 4 | a | + | 3 4 | − | 2 | a | × | 1 7 | + | 3 | × | 1 7 |
| = | 1 4 | a | + | 3 4 | − | 2 7 | a | + | 3 7 |
| = | - | 1 28 | a | + | 33 28 |
| - | 1 28 | a | + | 33 28 | = | 1 |
| - | 1 28 | a | = | 1 | − | 33 28 |
| - | 1 28 | a | = | - | 5 28 |
5 28 | = | 1 28 | a |
1 28 | a | = | 5 28 |
| a | = | 5 28 | ÷ | 1 28 |
| = | 5 28 | × | 28 |
| = | 5 | × | 1 |
| a | = | 5 |