为什么运行出来有错误

public class HelloWorld{

    public static void main(String[] args) {

   int one = 10 ;

        int two = 20 ;

        int three = 0 ;

        three=one+two;

        Syetem.out.println("three = one + two ==>"+three);

        three+=one;

        Syetem.out.println("three += one ==>"+three);

        three-=one;

        Syetem.out.println("three -= one ==>"+three);

        three*=one;

        Syetem.out.println("three *= one ==>"+three);

        three/=one;

        Syetem.out.println("three /= one ==>"+three);

        three%=one;

        Syetem.out.println("three %= one ==>"+three);

}

}

右边显示6 errors