Question

Three things you need in order to find a book in the library are ?

Answer 1

Dewey decimal classification
Call number
Category 

Answer 2

You need the dewy decimal system because you can use it to help you find if the book is there, you also need the last name to find the book, and you need to know if it is  a nonfiction book or a fiction book.
good luck! and i also hope this has helped you.