There are 3 ways Ruth can go from high school to the library, and 5 ways she can go from the library to her home.
The number of possible combinations is equal to the product between the options of each event (where the events are going from high school to the library and going from library to her house):
3*5 = 15
Then there are 15 different routes that Ruth can take from high school to her home, where she makes a stop at the library.
