| 序号 | 题目:1,2,9,12 | |
|---|---|---|
| 1 | ((12 + 2) + 9) + 1 | |
| 2 | ((12 + 9) + 2) + 1 | |
| 3 | ((12 + 1) + 2) + 9 | |
| 4 | ((12 + 2) + 1) + 9 | |
| 5 | ((12 + 9) + 1) + 2 | |
| 6 | ((12 + 1) + 9) + 2 | |
| 7 | (12 + 1) + (9 + 2) | |
| 8 | (12 + 9) + (2 + 1) | |
| 9 | (12 + (9 + 1)) + 2 | |
| 10 | (12 + (9 + 2)) + 1 | |
| 11 | (12 + (2 + 1)) + 9 | |
| 12 | (12 + 2) + (9 + 1) | |
| 13 | 12 + (9 + (2 + 1)) | |
| 14 | 12 + ((9 + 2) + 1) | |
| 15 | 12 + ((9 + 1) + 2) | |