Answer:
Yes, your total savings on gas is proportional to the number of beverages you purchase.
Step-by-step explanation:
What is a proportional relationship?
A proportional relationship, also known as direct relation, between two variables exists when the ratio between every pair of data is constant.
In this case the variables are:
number of beverage purchased
savings
Thus, as per every beverage purchase you save $ 0.20 the ratio of total savings to the number of beverage purchases is:
savings / beverages purchase = $ 0.20 / beverage
That means that you can determine the savings by multipliying the number of beverages times $ 0.20.
For proportional relationships it is easy to build a table that shows the behavior of the variables. This shows you that:
Number of beverages   savings    ratio
         1                              $ 0.20      $0.20 / 1 beverage = 0.20
         2                             $ 0.40      $0.40 / 2 beverages = 0.20
         3                             $ 0.60       $0.60 / 3 beverages = 0.20
         4                             $ 0.80       $0.80 / 4 beverages = 0.20