Why is this showing me wrong?

Question

I did the take a shortcut in c# I answered all questions but this question is showing me 24 wrong as answer. Why?
https://www.sololearn.com/post/505759/?ref=app

Answer 1

The out keyword causes arguments to be passed by reference.

static int Test(out int x, int y = 4){
x = 6;
return x * y;
}
static void Main(string[] args)
{
int a;
int z = Test(out a);
Console.WriteLine(a+z);
}

Explanation:
a is pass to Test as out in x parameter, in Test function, we have
x = 6 (since a is passed as out its value get changed to 6, because x and a are reference type any changes you make to x will change a also and vice versa)

Now Test returns x * y which 6 * 4 = 24 to the z variable in our main function.

therefore we have,
a = 6
z = 24

Console.WriteLine(6+24); ==> 30