Maybe it's a problem with your compiler? I don't know, this seems like pretty basic C++ so I would assume it shouldn't have any problems with the code. Here is exactly what I put into my compiler.
Code:
#include <iostream.h>
int main ()
{
int money;
int ihave = 188;
int lost;
cout << "Hur mycket pengar har du tjänat den här månaden?" << endl;
cin>>money;
cout << "Hur mycket pengar har du förlorat den här månaden?" << endl;
cin>>lost;
ihave -= lost;
ihave += money;
cout << "Så här mycket pengar har du nu!" << endl;
cout << ihave << endl;
return 0;
}