Right off the bat I can see that your function declaration of presentValue does not match up with your function definition. In your declaration, the parameters aren't really there, you just have the type, double, and no variable. Be sure to include the variables after the type in your declaration. Also, posting the error code or what it says would be helpful.
Remove the cout << from in front of presentValue(double numF, double numN, double numR) The presentValue function doesn't return a value, so you can't really use "cout" with it. If you wanted to do something like that you would have to change void to another type such as int, and have the function return a value. However it looks like your function should handle the printing to the screen by itself, so you just need to call the function.