Luis has $20.He buys 4 cans of tennis balls and gets $8 back as change .How much did one can of tennis balls cost?

Me. i can't figure out this question. give an explanation too. .

Which is the correct first step in finding the area of the base of a cylinder with a volume of 26x cubic meters and a height of 6.5 meters? v=bh 6.5=b(26x) v=bh v=26pi+(6.5) v=bh v=26pi(6.5) v=bh 26pi=b(6.5)

I’ve been trying all day to figure this puzzle out. i need the work for it aswell. it is a factoring polynomials tarsia. the image is below.