ok
divisible by 4 exactly measn that it is even
ends with 0,2,4,6,8
when you add 4 it divides by 5, if it is divisble by 5 it ends with 0 or 5
the possible numbers under 50 that are divisble by 5 are
5,10,15,20,25,30,35,40,45
if you add 4 to the mystery number, you get divisible by 5
minus 4 from all of that list and see which s divisible by 4
1,6,11,16,21,26,31,36,41
the number could be 16 or 36
