I'll give it a try, seems rather easy..
I think the first one is like this:
V=a*b*c
We know a=b
We know c=5
We know V=9245
9245=a*b*5
5ab=9245 / 5
ab=1849 (sqrt)
a=b=43
Since you cut 5 inches from each side, to form the edges for the box, the original piece has to be 10 inches wider .
43+10=53
P=53*53=2809 squareinches.