can you explaine me why the resulte is 1211

Question

#include <iostream>
using namespace std;

int main() {
int x=10;
int &y=x;
y++;
cout << x << y++;
return 0;
}

Answer 1

yeah it acts backwards. Try this:
int x = 0;
std::cout << x++ << x++ << x++;

You'll get 210.

Funny thing
std::cout << ++x << ++x << ++x;
will print 333

Answer 2

I think because cout using Insertion operator so that instructions work from right to left such that y++ run first then Value of y is Printed then Increased the value at y ( as using post increment) then print x ! ..