How to solve the below mentioned question?

Question

int &fun(){
static int x=10;
return x;
}
int main()
{
fun()=30;
cout<<fun();

}

Answer 1

https://stackoverflow.com/questions/18964801/assigning-value-to-function-returning-reference

Answer 2

Which question?

Answer 3

I don't get it. I just see a small code. What do you want to know about it?