How do you solve this problem?

9514 1404 393
Answer:
-19.2
Step-by-step explanation:
Fill in the given values and do the arithmetic.
[tex]\displaystyle x\ \blacksquare\ y=\frac{x}{y}-xy\\\\4\ \blacksquare\ 5=\frac{4}{5}-4\cdot5=0.8-20\\\\\boxed{4\ \blacksquare\ 5=-19.2}[/tex]