The ratio of the number of adults to the number of children in a library is 12:5. If there are 45 children in the library, how many adults are there at the library?
This can be solved with a simple proportion. 5/12 = 45/1. For 5 to become 45, you need to multiply by 9. You do the same to the denominator. 12 times 9 is 108.
