Well, you are currently prototyping quite a lot of functions in the middle of your main() routine.
Perhaps you could try thinking of functions as individual chapters of a reference book.
Your list of function prototypes goes at the start (like a contents index).
Each "function" is then like a separate chapter - you can't put one chapter inside another.
I would write this code slowly, from scratch, entering one new function at a time, rather than trying to write the whole in one go.
in these lines, you create function prototypes, but I do not see the definition of the functions, that is, when they are called those functions do not produce any effect as they have no code inside (if the compiler will accept them)
double displayMenuGetValidPassType()
{
std::cin >> passType ; // insert the value for var passType
switch (passType)
{
case 1:
baseCost = OP;
passName = "One Park One Day Pass";
break;
case 2:
baseCost = PH;
passName = "Park Hopper Pass";
break;
case 3:
baseCost = PHWP;
passName = "One Park One Day Pass with Water Part Option";
break;
case 4:
baseCost = PHWP;
passName = "Park Hopper Pass with Water Park Option";
break;
case 5:
amtDue = AP; //supposed to be done in main, but you are stupid and dont know how to do this
baseCost = AP;
passName = "Annual Pass";
numDays = 365;
break;
default:
validPassType = false;
break;
}
return ??? (double type)
}