Calculus word problems

Question

The national average price of gas is the us was $3.60 per gallon during the summer of 2014. During the summer of 2015, the natiional average price was about $2.60 per gallon. Find the relative change in the price of a gallon of gas between the summer of 2014 and the summer of 2015.

Answer 1

price 15 = 2.60  - price 14 = 3.60 = $ -1

so (-1/3.60)100 = (-0.27777)100 = -27.777%