C++ :: How To Store A Score

I want to do something like when you have completed the first question then the program will give you +3 in coins then you have completed next question then I want the program to add 3 more so it says you have a value of coins 6. But I do not know exactly how to do this the code I begun to write was this:

Code:
#include <iostream>
using namespace std;
int main()

[Code] ...

This code works for 1 question but I want it to work like add 3 for every question the user guesses correct. Like if user enters the correct answer 3 times then he/she has a value of coins 9.