The formula for finding the volume of a cube is

, where s is the side length.
The formula for a cube with each side length doubled is

, or 8<span>s.
</span><span>If all the dimensions of a cube are doubled, then the new volume is
eight times greater.</span>
I don't understand what you're asking, is there supposed to be a picture with the question?
Answer 6 hours
Reason
7x + 9.50 = 55
-9.50. -9.50 subtract from both sides
_____________
7x = 45.50
Divide both sides by 7 to isolate x
X = 6.5
So he can rent for 6 hours (the .5 would be charged as a full hour per the problem)