两道数学题，谁给指点一下迷经？

1, If n is a positive integer and n平方 is divisible by 72,then the largest positive integer that must divide n is $ a" }( f+ X6 q5 [3 _% d5 Y

: s: j6 s3 ]2 t# w0 l& C0 r8 C0 AA 6  B 12 C 24 D 36 E 48
2 c/ L; ^- j" e$ a/ C
  ?/ {/ k. a* R# N2 C1 w4 R6 t, k* Y. i, W7 y
2 , a survey of 100 persons revealed that 72 of them had eaten at restaurant P and that 52 of them had eaten at restaurant Q,which of the following could not be the number of persons in the surveyed group who had eaten at both P and Q
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a 20 b 24 c 30 d 50 e 52
9 x; q' g& j- ?9 w( q' x  {8 M2 Z2 r* I3 {3 t  H

; F$ D; u6 p: c& M谁能告诉我上面两道题的正确翻译和解题思路。谢谢