The trick is understanding how to translate a mathematical formula into code. The conversion formula needs to be written exactly as shown, respecting operator precedence.
Multiplication and division happen before addition. I'll show you why data types matter. If you write 9/5 with integers, you get 1 instead of 1.8 because integer division truncates. You need at least one operand to be a double, so write 9.0/5 or 9/5.0.
You also need to format the output correctly. The problem asks for 2 decimal places, so you'll use fixed and setprecision from the iomanip library.