| ( | ( | a | + | 1 | ) | ÷ | 4 | ) | = | a | + | 1 | − | ( | 5 | a | − | 1 | ) | ÷ | 12 |
| 方程左边 = | ( | a | + | 1 | ) | ÷ | 4 |
| = | a | × | 1 4 | + | 1 | × | 1 4 |
| = | a | × | 1 4 | + | 1 4 |
1 4 | a | + | 1 4 | = | a | + | 1 | − | ( | 5 | a | − | 1 | ) | ÷ | 12 |
| 方程右边 = | a | + | 1 | − | 5 | a | × | 1 12 | + | 1 | × | 1 12 |
| = | a | + | 1 | − | 5 12 | a | + | 1 12 |
| = | 7 12 | a | + | 13 12 |
1 4 | a | + | 1 4 | = | 7 12 | a | + | 13 12 |
1 4 | a | − | 7 12 | a | = | 13 12 | − | 1 4 |
| - | 1 3 | a | = | 13 12 | − | 1 4 |
| - | 1 3 | a | = | 5 6 |
| - | 5 6 | = | 1 3 | a |
1 3 | a | = | - | 5 6 |
| a | = | - | 5 6 | ÷ | 1 3 |
| = | - | 5 6 | × | 3 |
| = | - | 5 2 | × | 1 |
| a | = | - | 5 2 |
| a | = | - 2.5 |