public class Calculator {
  public static void main(String[] args) {
    double a = 10.0, b = 20.0, c;
    c = add(a, b);
    System.out.println(a + " + " + b + " = " + c);
    c = subtract(a, b);
    System.out.println(a + " - " + b + " = " + c);
    c = multiply(a, b);
    System.out.println(a + " * " + b + " = " + c);
    c = divide(a, b);
    System.out.println(a + " / " + b + " = " + c);
  }
  
  public static double add(double x, double y) {
    return x + y;
  }
  public static double subtract(double x, double y) {
    return x - y;
  }
  public static double multiply(double x, double y) {
    return x * y;
  }
  public static double divide(double x, double y) {
    return x / y;
  }
}