Answer :
To arrange cadets in desired arrangement we make prime factors of 72 ( Number of cadets ) .
72 = 2 2 2 3 3
So,
We can see that only at
8 9 = 72
We get , Number of column and number of rows have more than 6 cadets .
And
Column = 9 So, rows = 8 , So, That is also satisfied the second condition .
So,
Number of rows = 8 ( Ans )