3,6,7,9\24点

1:3 - (6 - 9) × 7
2:3 - ((6 - 9) × 7)
3:3 × (6 + 9 - 7)
4:3 × ((6 + 9) - 7)
5:3 × (6 + (9 - 7))
6:3 × (6 - 7 + 9)
7:3 × ((6 - 7) + 9)
8:3 × (6 - (7 - 9))
9:3 + (9 - 6) × 7
10:3 + ((9 - 6) × 7)
11:3 × (9 + 6 - 7)
12:3 × ((9 + 6) - 7)
13:3 × (9 + (6 - 7))
14:3 × (9 - 7 + 6)
15:3 × ((9 - 7) + 6)
16:3 × (9 - (7 - 6))
17:3 - (7 × (6 - 9))
18:3 - 7 ×(6 - 9)
19:3 × 7 - 6 + 9