couts/cins を削除すると、エラーはなくなります。
std::basic_istream<_CharT, Traits>:: _istream_type& std::basic_istream<_CharT, _Traits>::operator>>(long double&) [with _CharT = char, _Traits = std::char_traits, std::basic_istream<_CharT, Traits>:: _istream_type = std::basic_istream]
コードは次のとおりです。
#include <iostream>
#include <string>
using namespace std;
int main()
{
int x;
int y;
int z;
cout << "Enter number of girrafes" << endl;
cin >> x >> endl;
cout << "Enter number of elephants" << endl;
cin >> y >> endl;
cout << "Enter number of tigers" << endl;
cin >> z >> endl;
}