The cost per person for the bus rental varies inversely to the number of people going on the trip. It will cost $25 per person if 45 people go on the trip. How much will it cost per person if 30 people go on the trip?

The first thing we are going to do to solve this problem, is setting up our proportion:
[tex] \frac{25----\ \textgreater \ 45people}{x-----\ \textgreater \ 30people} [/tex]
[tex] \frac{25}{x} = \frac{45}{30} [/tex]

Since the cost per person for the bus rental varies inversely to the number of people going on the trip, we are going to invert our second fraction and solve for [tex]x[/tex]:
[tex] \frac{25}{x} = \frac{30}{45} [/tex]
[tex] \frac{25}{30} = \frac{x}{45} [/tex]
[tex]x= \frac{(25)(45)}{30} [/tex]
[tex]x= \frac{1125}{30} [/tex]
[tex]x=37.5[/tex]

We can conclude that it will cost $37.5 per person if 30 people go on the trip.