; on if is wrong, so is the direction of your operators on the cin lines. Also sign should be a char and encased in '' not "", heres a fixed version.
Code:
#include <iostream>
using namespace std;
int main()
{
cout << "Stephen's C++ Calculator" << endl;
cout << "Enter a number" << endl;
int a;
cin >> a;
cout << a << endl;
cout << "Now push a math sign" << endl;
char sign;
cin >> sign;
cout << a <<" "<< sign << endl;
cout << "Now push a second number" << endl;
int b;
cin >> b;
if (sign == '+')
{
int resultplus;
resultplus = a + b;
cout << resultplus << " is your answer!" << endl;
}
if(sign == '-')
{
int resultminus;
resultminus = a - b;
cout << resultminus << " is your answer!" << endl;
}
if(sign == '/')
{
int resultdivide;
resultdivide = a / b;
cout << resultdivide << " is your answer!" << endl;
}
if(sign == '*')
{
int resultmultiply;
resultmultiply = a*b;
cout << resultmultiply << " is your answer!" << endl;
}
return 0;
}