[tex]\begin{gathered} \text{Let y represent the number of of non fiction books in the library} \\ \text{The number of fiction books = }\frac{2}{5}y \\ \text{Total books = 56} \\ y\text{ + }\frac{2y}{5}\text{ = 56} \\ \text{ multiply through by 5} \\ 5y+2y=280 \\ 7y=280 \\ y=\frac{280}{7} \\ y=40 \end{gathered}[/tex]
Number of fiction books = 2/5 x 40 = 16 books
