Can't call function in C#

Im trying to call this calculator function:

public static void Main(string[] args) {
    int answer = calculate(int a, int b);
    Console.WriteLine(answer);
}

public int calculate(int a, int b) {
    return a + b;
}

but I keep getting an error about making a non-static reference

>Solution :

The reason you can’t call your function is because you can’t call a non static function from a static function, try adding the static keyword to your calculate function header