Answer:
3.333
C = 3.3333g
Explanation:
Given the relation : C = rg
C = Total cost of gasoline
g = Number of gallons of gasoline used
r = constant of proportionality
Picking any point on the graph :
At cost, c = $30
Number of gallons of gasoline used, g = 9
Putting the values into our equation :
C = rg
$30 = r * 9
30 = 9r
Divide both sides by 9
30/9 = 9r / 9
3.333 = r
Hence, constant of proportionality, r = 3.333