The answer to your question is 7.94 that the perfect square root of 63
You could use the Pythagorean theorem which is a squared +b squared= c squared
you know a and c
a=24
c=25
24 squared + x squared = 25 squared
576+x squared =625
subtract 576 from both sides
x squared = 49
square root x and 49
x=7
C is the answer
2. 2 x (12 x 6) + 2 x (15 x 6) + 2 x (12 x 15) = 684