由9 7 5 4组成的24点等式全部如下，
1: 4 × 7 + 5 - 9
2: (4 × 7) + 5 - 9
3: (4 × 7 + 5) - 9
4: ((4 × 7) + 5) - 9
5: 4 × 7 +(5 - 9)
6: (4 × 7) + (5 - 9)
7: 4 × 7 - 9 + 5
8: (4 × 7) - 9 + 5
9: (4 × 7 - 9) + 5
10: ((4 × 7) - 9) + 5
11: 4 × 7 -(9 - 5)
12: (4 × 7) - (9 - 5)
13: 4 × 9 -(5 + 7)
14: (4 × 9) - (5 + 7)
15: 4 × 9 - 5 - 7
16: (4 × 9) - 5 - 7
17: (4 × 9 - 5) - 7
18: ((4 × 9) - 5) - 7
19: 4 × 9 -(7 + 5)
20: (4 × 9) - (7 + 5)
21: 4 × 9 - 7 - 5
22: (4 × 9) - 7 - 5
23: (4 × 9 - 7) - 5
24: ((4 × 9) - 7) - 5
25: 5 + 4 × 7 - 9
26: (5 + 4 × 7) - 9
27: (5 + (4 × 7)) - 9
28: 5 + (4 × 7) - 9
29: 5 + (4 × 7 - 9)
30: 5 + ((4 × 7) - 9)
31: 5 + 7 × 4 - 9
32: (5 + 7 × 4) - 9
33: (5 + (7 × 4)) - 9
34: 5 + (7 × 4) - 9
35: 5 + (7 × 4 - 9)
36: 5 + ((7 × 4) - 9)
37: (5 × (7 - 4)) + 9
38: 5 × (7 - 4) + 9
39: 5 - 9 + 4 × 7
40: (5 - 9) + 4 × 7
41: 5 - 9 +(4 × 7)
42: (5 - 9) + (4 × 7)
43: 5 - (9 - 4 × 7)
44: 5 - (9 - (4 × 7))
45: 5 - 9 + 7 × 4
46: (5 - 9) + 7 × 4
47: 5 - 9 +(7 × 4)
48: (5 - 9) + (7 × 4)
49: 5 - (9 - 7 × 4)
50: 5 - (9 - (7 × 4))
51: (7 - 4) × 5 + 9
52: ((7 - 4) × 5) + 9
53: 7 × 4 + 5 - 9
54: (7 × 4) + 5 - 9
55: (7 × 4 + 5) - 9
56: ((7 × 4) + 5) - 9
57: 7 × 4 +(5 - 9)
58: (7 × 4) + (5 - 9)
59: 7 × 4 - 9 + 5
60: (7 × 4) - 9 + 5
61: (7 × 4 - 9) + 5
62: ((7 × 4) - 9) + 5
63: 7 × 4 -(9 - 5)
64: (7 × 4) - (9 - 5)
65: (7 × (9 - 5)) - 4
66: 7 × (9 - 5) - 4
67: 9 × 4 -(5 + 7)
68: (9 × 4) - (5 + 7)
69: 9 × 4 - 5 - 7
70: (9 × 4) - 5 - 7
71: (9 × 4 - 5) - 7
72: ((9 × 4) - 5) - 7
73: 9 - (4 - 7) × 5
74: 9 - ((4 - 7) × 5)
75: 9 × 4 -(7 + 5)
76: (9 × 4) - (7 + 5)
77: 9 × 4 - 7 - 5
78: (9 × 4) - 7 - 5
79: (9 × 4 - 7) - 5
80: ((9 × 4) - 7) - 5
81: 9 - (5 × (4 - 7))
82: 9 - 5 ×(4 - 7)
83: 9 + (5 × (7 - 4))
84: 9 + 5 ×(7 - 4)
85: (9 - 5) × 7 - 4
86: ((9 - 5) × 7) - 4
87: 9 + (7 - 4) × 5
88: 9 + ((7 - 4) × 5)
你给的顺序无解
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