Question

31
85
90
21
41
45
47
69
20
83
59
35
34
88
15
80
12
89
51
31
77
94
84
18
21
12
24
52
55
75
21
41
20
74
90
26
19
12
99
19
??

try all mathematically ways and find out the answer????

Answer 1

3 is the answer because