| 序号 | 题目：5,7,9,13 | |
|---|---|---|
| 1 | ((13 + 7) + 9) − 5 | |
| 2 | ((13 + 9) + 7) − 5 | |
| 3 | ((9 + 7) + 13) − 5 | |
| 4 | ((13 + 9) − 5) + 7 | |
| 5 | ((13 + 7) − 5) + 9 | |
| 6 | ((13 − 5) + 7) + 9 | |
| 7 | (13 + (9 − 5)) + 7 | |
| 8 | (13 − 7) × (9 − 5) | |
| 9 | (13 + 9) + (7 − 5) | |
| 10 | (13 + 7) + (9 − 5) | |
| 11 | (9 + (13 − 5)) + 7 | |
| 12 | (9 + 7) + (13 − 5) | |
| 13 | (13 + (7 − 5)) + 9 | |
| 14 | 13 + (7 + (9 − 5)) | |
| 15 | 13 + ((9 + 7) − 5) | |
| 16 | 13 + (9 + (7 − 5)) | |