If an ostrich can run 50 miles in one hour then he can run 12.5 miles in 15 minutes. 15 minutes is 1/4 of an hour. Multiply 50 by 0.25 = 15.
#1 There is no area of a cube. There is only a volume.
#2 The formula is

where s is the side.
Substitute 729 in V since that is the volume.

Take the cube root and you will get
9.
So the formula is
and the side is 9.
Its 90 because its a L shaped will means its 90
Use the property of distribution:
a(b+c) = ab + ac
4(4a+5) = 4(4a) + 4(5)
4(4a+5) = 16a + 20
Hope that helps :)