5,6,6,9的24点答案：
1:6 × 9 - 5 × 6
2:(6 × 9) - 5 × 6
3:6 × 9 -(5 × 6)
4:(6 × 9) - (5 × 6)
5:6 × 9 - 6 × 5
6:(6 × 9) - 6 × 5
7:6 × 9 -(6 × 5)
8:(6 × 9) - (6 × 5)
9:9 × 6 - 5 × 6
10:(9 × 6) - 5 × 6
11:9 × 6 -(5 × 6)
12:(9 × 6) - (5 × 6)
13:9 × 6 - 6 × 5
14:(9 × 6) - 6 × 5
15:9 × 6 -(6 × 5)
16:(9 × 6) - (6 × 5)