I can see four major problems here:

#1: You have set NUM_HRS as a "const int", which means it is "constant", which means it can NEVER change its value. You DO change it when you convert the minutes to hours.

#2: Your final else statement doesn't have any braces. Without these, it only performs the first line after it, which I think isn't what you want.

#3:
Code:
(NUM_HRS - FREE_TRUCK) * TRUCK_RATE;
does not assign to anything. In otherwords, you need to have an equals sign somewhere.

#4:
Code:
cout << Veh_Type == "Truck";
This will probably not do what you think. This will output either a 1 or 0 to the screen. What it is saying is "Is Veh_Type a "Truck"", and it will respond with either yes (1) or no (0).

#5: Veh_Type is a char type, meaning that it holds only ONE character. "Truck" is, at least, 5. Change Veh_Type to a std::string or char array.

Here's a rough overview of the differences between strings and chars:
Strings are WORDS or SENTENCES that can be of any length. Chars are of only one character, for example, 'A' or '6' or '%' are all a char. Chars aren't super useful, but you can have many chars in an array. An array can look like this:

Code:
char TESTWORD[20];
This is pretty much the same as a string, except it is limited to only 20 characters.

There are a couple of other little things... but that should be a big enough load for now.