Hi there! 5 bottles of water for $3 would make $0.60 per bottle. 0.6 * 15 = 9. That means 15 bottles of water should equal $9, but instead it is $8. Based on that, no. The costs for bottles of water is not proportional to the numbers sold. Basically, you can divide to find unit prices and multiply the number of another item to see if the numbers are proportional.
