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