| 12 | ( | 2 | ÷ | 3 | × | a | × | 3 | ÷ | 5 | ) | + | 16 | ( | 1 | ÷ | 3 | × | a | × | 1 | ÷ | 2 | ) | = | 16 | ( | 2 | ÷ | 3 | × | a | × | 2 | ÷ | 5 | ) | + | ( | 1 | ÷ | 3 | × | a | × | 1 | ÷ | 2 | ) |
| 方程左边 = | 12 | × | 2 | ÷ | 3 | × | a | × | 3 | ÷ | 5 | + | 16 | ( | 1 | ÷ | 3 | × | a | × | 1 | ÷ | 2 | ) |
| = | 24 5 | a | + | 16 | ( | 1 | ÷ | 3 | × | a | × | 1 | ÷ | 2 | ) |
| = | 24 5 | a | + | 16 | × | 1 | ÷ | 3 | × | a | × | 1 | ÷ | 2 |
| = | 24 5 | a | + | 8 3 | a |
| = | 112 15 | a |
112 15 | a | = | 16 | ( | 2 | ÷ | 3 | × | a | × | 2 | ÷ | 5 | ) | + | ( | 1 | ÷ | 3 | × | a | × | 1 | ÷ | 2 | ) |
| 方程右边 = | 16 | × | 2 | ÷ | 3 | × | a | × | 2 | ÷ | 5 | + | ( | 1 | ÷ | 3 | × | a | × | 1 | ÷ | 2 | ) |
| = | 64 15 | a | + | ( | 1 | ÷ | 3 | × | a | × | 1 | ÷ | 2 | ) |
| = | 64 15 | a | + | 1 | ÷ | 3 | × | a | × | 1 | ÷ | 2 |
| = | 64 15 | a | + | 1 6 | a |
| = | 133 30 | a |
112 15 | a | = | 133 30 | a |
112 15 | a | − | 133 30 | a | = | 0 |
91 30 | a | = | 0 |
| a | = | 0 | ÷ | 91 30 |
| = | 0 | × | 30 91 |
| a | = | 0 |