int bla(int x, int &y)
{
  x = x+y;
  y = 7;
  return y;
}

...

   int a,b,c;
   a = 1;
   b = 2;
   c = bla(a,b);
// here

Answer:
a == 1
b == 7
c == 7

...

int blup(int &x, int &y)
{
   x = 7;
   return y;
   y = 5;
}
...
   int d,e,f;
   d = 1;
   e = 2;
   f = blup(d,e);
// here

Answer:
d == 7
e == 2
f == 2