Answer:
slope= - 0.175 and is average decrease of price of gas per gallon per year
Step-by-step explanation:
slope= (y2-y1)/(x2-x1)
slope = (2.80-3.50)/(2018-2014)
slope= -0.7/4
slope= - 0.175
as along y axis it is average gas price per gallon and along x axis it is time in years and in gradient or slope both change so gradient is change in average gas price per gallon per year as it is negative so it shows average decrease of price of gas per gallon per year