In one day a movie store rented out 20 comedies. if the ratio of comedies rented to action movies rented was 4: 3, how many action movie were rented ?

The answer is 15 action movies were rented

One way to solve is to set up a proportion. If the ratio of comedies to action is 4:3 (also can be written as the fraction 4/3) then you can set 4/3 equal to 20/x.

4/3 = 20/x

then cross multiply.  

4·x = 3·20

4x = 60  Then divide both sides by 4

x= 15 

J= r + 9 because since jessica rode 9 more miles than roger, you add 9 miles to rogers mileage.