4、5、7、6算24点

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

(6-4)*(5+7)
4+5+7+6

4*(5+7-6)=4*6=24

(5+7)(6-4)
4*(5+7-6)

7减6加5,乘4

4×(5+7-6)=4×6=24