Declair a variable

[cibide]

Guys, sorry to bother but can anyone explain me how I should declair x variable in this case? I am always having problems with it and I cant find a solution...

  #include "stdafx.h"
#include <iostream>

void IsEven()
{
	using namespace std;
	int x, y = 8;
	if(x %= y)
		cout << "true" << endl;
	else
		cout << "false" << endl;
}

int main()
{
	using namespace std;
	cout << "enter a number: ";
	cin >> x;
	cout << endl;
	IsEven();
	system("pause");
	return 0;
}

[ne555]

#include <iostream>
bool IsEven(int x){
   return x%2 == 0;
}

int main(){
   int x, foo, the_name_is_irrelevant;
   std::cin >> x >> foo >> the_name_is_irrelevant;
   std::cout << std::boolalpha;
   std::cout << IsEven(x) << '\n';
   std::cout << IsEven(foo) << '\n';
   std::cout << IsEven(the_name_is_irrelevant) << '\n';
}

[cibide]

ok ty!