4.7.8.9算24点

(9/(7-4))*8=24

4*（7+8-9〕=24

8*[9/(7-4)]=24

1: 4 × (7 + 8 - 9)
2: 4 × ((7 + 8) - 9)
3: 4 × (7 + (8 - 9))
4: 4 × (7 - 9 + 8)
5: 4 × ((7 - 9) + 8)
6: 4 × (7 - (9 - 8))
7: 4 × (8 + 7 - 9)
8: 4 × ((8 + 7) - 9)
9: 4 × (8 + (7 - 9))
10: (4 + 8) × (9 - 7)
11: 4 × (8 - 9 + 7)
12: 4 × ((8 - 9) + 7)
13: 4 × (8 - (9 - 7))
14: (7 + 8 - 9) × 4
15: ((7 + 8) - 9) × 4
16: (7 + (8 - 9)) × 4
17: (7 - 9 + 8) × 4
18: ((7 - 9) + 8) × 4
19: (7 - (9 - 8)) × 4
20: (8 + 4) × (9 - 7)
21: (8 ÷ (7 - 4)) × 9
22: 8 ÷ (7 - 4) × 9
23: 8 ÷ ((7 - 4) ÷ 9)
24: (8 + 7 - 9) × 4
25: ((8 + 7) - 9) × 4
26: (8 + (7 - 9)) × 4
27: (8 - 9 + 7) × 4
28: ((8 - 9) + 7) × 4
29: (8 - (9 - 7)) × 4
30: 8 × (9 ÷ (7 - 4))
31: 8 × 9 ÷(7 - 4)
32: (8 × 9) ÷ (7 - 4)
33: (9 - 7) × (4 + 8)
34: (9 ÷ (7 - 4)) × 8
35: 9 ÷ (7 - 4) × 8
36: 9 ÷ ((7 - 4) ÷ 8)
37: (9 - 7) × (8 + 4)
38: 9 × (8 ÷ (7 - 4))
39: 9 × 8 ÷(7 - 4)
40: (9 × 8) ÷ (7 - 4)

7-(9-8))*4