help having trouble, its quite easy.

I believe it's C because 15 with an exponent of 5 is 15 x 15 x 15 x 15 x 15.
So that's basically larger than 15 x 15 x 15 x 15.
Common sense.
C because 15 over 5 is equal to 15 five times and in C it is shown only 4 times so 15 over 5 <15 over 4. (C)