Five sets of ear buds cost $53.15. How much will 9 sets of ear buds cost?

Five sets of ear buds cost $53.15. How much will 9 sets of ear buds cost?

Set up a proportion of earbuds to cost where c is the cost of 9 ear buds:
5/53.15 = 9/c

To solve this proportion for c, we type it in our math engine and we get:
c = 95.67