| 1 | ÷ | 60 | × | 20 | + | ( | 1 | ÷ | 60 | + | 1 | ÷ | 90 | ) | A | = | 1 |
| 方程左边 = | 1 3 | + | ( | 1 | ÷ | 60 | + | 1 | ÷ | 90 | ) | A |
1 3 | + | ( | 1 | ÷ | 60 | + | 1 | ÷ | 90 | ) | A | = | 1 |
| 方程左边 = | 1 3 | + | 1 | ÷ | 60 | × | A | + | 1 | ÷ | 90 | × | A |
| = | 1 3 | + | 1 60 | A | + | 1 90 | A |
| = | 1 3 | + | 1 36 | A |
1 3 | + | 1 36 | A | = | 1 |
1 36 | A | = | 1 | − | 1 3 |
1 36 | A | = | 2 3 |
| A | = | 2 3 | ÷ | 1 36 |
| = | 2 3 | × | 36 |
| = | 2 | × | 12 |
| A | = | 24 |