Answer:
There are 16 fiction books in the library.
Step-by-step explanation:
We are given the following in the question:
Let x be the number of fiction books and y be the number of non fiction books.
Total number of books = 56
Thus, we can write the equation:

There are
as many fiction books as there are nonfiction books.
Thus, we can write the equation:

Solving the two equations by substitution, we get,

Thus, there are 40 non fiction books.
Number of fiction books =

Thus, there are 16 fiction books in the library.