The x is 8-7=1 your welcome
That is right because it has 5 so it could be 4.8 and/or 4.9
The ratio of the surface areas of similar solids is equal to the square of their scale factor and that the ratio of their volumes is equal to the cube of their scale factor.
Did you try the square root of 4? 2?
You would need too do 5*5=25 if you did 5*7=35 that would be wrong