What was the drivers change in the elevation in each interval

How can you decide witch operations to use to slice a two step equation

Jackie purchased 3 bottles of water and 2 cups of coffee for the family for $7.35. ryan bought 4 bottles of water and 1 cup of coffee for his family for 7.15. how much does each bottle of water cost? how much does each cup of coffee cost?

Do, h = (7, 9) (14, 18) the scale factor is