Answer:
-17 (I believe)
Step-by-step explanation:
If x = 64 then the first one is asking for the square root of 64 (8)
With y being 25 the second part of this problem is actually really easy, all its doing is getting the square root and then squaring it (doing nothing at all) so that would just be 25 which would make it
8-25 which would be -17