Answer:
9^2= 81, √25= 5, 21^2= 441, √4= 2, √144= 12, 16^2= 256, √625= 25, (-11)^2=121
64/4 is 16 if that's what you meant.
I believe the answer is C
For this case we must find an expression equivalent to:

We look for the factors of 10 and 30:
10: 1,2,5,10
30: 1,2,3,5,6,10,15,30
The greatest common factor of both numbers is 10.
Then, we can rewrite the expression as:

Answer:

There are 6/10 left over. 6/10 reduces to 3/5.