2.6.7.1算24

共有4种形式：
1、2*(6+7-1)=24
2、6*(7-1-2)=24
3、(6-2)*(7-1)=24
4、6*(1+7)/2=24

(7+6-1)×2=24
（7+1）×（2+6）=24
（7-1-2）×6=24
（6÷2）×（7+1）=24
（6-2）×（7-1）=24
（7+1）÷2×6=24
(7-1+6)×2=24
(7+1)×6÷2=24

1: 2 × (6 + 7 - 1)
2: 2 × ((6 + 7) - 1)
3: 2 × (6 + (7 - 1))
4: (2 - 6) × (1 - 7)
5: 2 × (6 - 1 + 7)
6: 2 × ((6 - 1) + 7)
7: 2 × (6 - (1 - 7))
8: 2 × (7 + 6 - 1)
9: 2 × ((7 + 6) - 1)
10: 2 × (7 + (6 - 1))
11: 2 × (7 - 1 + 6)
12: 2 × ((7 - 1) + 6)
13: 2 × (7 - (1 - 6))
14: (6 - 2) × (7 - 1)
15: 6 ÷ 2 ×(7 + 1)
16: (6 ÷ 2) × (7 + 1)
17: 6 ÷ (2 ÷ (7 + 1))
18: 6 ÷ 2 ×(1 + 7)
19: (6 ÷ 2) × (1 + 7)
20: 6 ÷ (2 ÷ (1 + 7))
21: 6 × (7 - (2 + 1))
22: 6 × (7 - 2 - 1)
23: 6 × ((7 - 2) - 1)
24: (6 + 7 - 1) × 2
25: ((6 + 7) - 1) × 2
26: (6 + (7 - 1)) × 2
27: (6 × (7 + 1)) ÷ 2
28: 6 × (7 + 1) ÷ 2