求大神解答，怎么错的？

public class HelloWorld{
    public static void main(String[] args) {
     int one = 10 ;
        int two = 20 ;
        int three = 0 ;
        there=one+two;
        System.out.println("there=one+two==>"+there);
        there+=one;
        System.out.println("there+=one==>"+there);
        there-=one;
        System.out.println("there-=one==>"+there);
        there*=one;
        System.out.println("there*=one==>"+there);
        there/=one;
        System.out.println("there/=one==>"+there);
        there%=one;
        System.out.println("there%=one==>"+there);
  
 }
}