#include <iostream>
using namespace std;

int main()
{
	int x,y;
	cout << "Nhap x: "; cin >> x;
	cout << "Nhap y: "; cin >> y;
	double d = static_cast<double>(n1) / n2;

	cout << d << endl;

	return 0;
}

In function 'int main()':
Line 9: error: 'n1' was not declared in this scope
compilation terminated due to -Wfatal-errors.