7,8,10,9的24点答案：
1:(8 ÷ (10 - 7)) × 9
2:8 ÷ (10 - 7) × 9
3:8 ÷ ((10 - 7) ÷ 9)
4:8 × (9 ÷ (10 - 7))
5:8 × 9 ÷(10 - 7)
6:(8 × 9) ÷ (10 - 7)
7:9 × (8 ÷ (10 - 7))
8:9 × 8 ÷(10 - 7)
9:(9 × 8) ÷ (10 - 7)
10:(9 ÷ (10 - 7)) × 8
11:9 ÷ (10 - 7) × 8
12:9 ÷ ((10 - 7) ÷ 8)