3.5 is the answer
I did the math and that is what i got.
Answer:
I would try going with 12.2
Step-by-step explanation:
If I'm correct this is very simple.
x=15
So plug that into the equation and you get
11.00+0.08x15
which equals 12.2
So I recommend trying that out :)

Actually Welcome to the concept of Surface Areas and Volume.
==> Volume of Cylinder = πr^2h
==> 27π = πr^2(3)
==> 27 = r^2 (3)
==> r^2 = 9
==> r = 3 inch
hence the radius is 3 inches.
Based on the info given the answer is ∞