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!