The answer is 15
From the graph:
Car A traveled 60 miles in one hour
Car B traveled 75 miles in one hour.
Car B travels 15 more miles per hour
It would take her 12 minutes because if you mutipy 2/3 by 3/2 then you get 1 (as in one mile) and then you have to do that to the other side too so then you multiply 8 by 2/3 and get 12
It is true the relationship is proportional.
hope this helps!!