Answer
See graph.
\begin{cases} x+y\leq100\hspace2cm(total-books) \\ y\geq20\hspace2cm(minimum- nonfiction)\\x\geq y \\x\geq0, y\geq0\end{cases}
Work Step by Step
Step 1. Assume the $x$ number of fiction books and $y$ number of nonfiction books,
Step 2. Set up the inequalities based on the given conditions:
\begin{cases} x+y\leq100\hspace2cm(total-books) \\ y\geq20\hspace2cm(minimum- nonfiction)\\x\geq y \\x\geq0, y\geq0\end{cases}
Step 3. We can graph the solution set as shown (solution region).
