Output please explain me

Question

int x(int &a, int &b)
{a=3;b=4;return a+b;}
int main()
{
int a=2;
int b=7;
int c=x(a,a);
cout<<a<<b<<c;
return 0;
}
output 478
my guess 477

Answer 1

When you send data a to function x. At first line value of a become 3. On second line its value change to 4. and there is only one variable send. When it write a+b that mean it access only one variable address that is a.
here a+b become a+a
And thus it return 8.
So value of
a=4
b=7 (does not change because it is not send to function)
c=8

Answer 2

thanks I missed that only one variable was sent so a+b will be a+a