A group of college friends plan to rent a house together for x dollars per month, which is to be shared equally among them. If four, rather than five people rent the house together, how many more dollars, in terms of x, will each person have to pay for rent per month? Pick one:
A) x/4  B) x/5  C) x/9  D) x/20  E) 4x/9
If 5 people share the rent, each person would pay x/5.   If 4 people share the rent, each person will pay x/4.   The extra amount each person pays is x/4 - x/5 = 5x/20 - 4x/20 = x/20   The answer is x/20.
<result>D</result>
A group of college friends plan to rent a house together for x dollars per month, which is to be shared equally among them. If four, rather than five people rent the house together, how many more dollars, in terms of x, will each person have to pay for rent per month?