Now I found it thanks Qyther and Gami

Question

make it correct
https://code.sololearn.com/cMQ7tVsdTiCu/?ref=app

Answer 1

Your errors are on lines 3 and 4. a and b are not passed in the functions. Make sure you include parameters in the function definition:

public static void horn(int a, int b)

For the function to work, you need values for a and b, which are called arguments. To do that change line 13 to:

Vehicle.horn(a, b)

Answer 2

initialize variables

public static void horn() {
int a = 0;
int b = 0;

a =a+1;
b =b*2;
System.out.println(a+" "+" "+b);
}