You can buy an 8-pack of paper towels for 77.92 or a 12-pack for 11.64. which is a better buy?

First, you would need to create equations to figure out how much a single roll of paper towel would cost from each pack. 
8-pack: $7.92 ÷ 8 = $0.99
12-pack: $11.64 ÷ 12 = $0.97

Now, all you would have to do is subtract to find the difference. 
$0.99 - $0.97 = $0.02

The 12-pack is 2 cents cheaper per roll than an 8-pack. The 12-pack would be a better deal. 

I hope this helps!

113.1, but it is not there, so probably choose 113.04. whatever your teacher is using to calculate is weird

Step-by-step explanation:

2πrh+2πr2 is the formula.