finished

src/App.java

 public class App {
     public static void main(String[] args) throws Exception {
-        System.out.println("Hello, World!");
+    	Complex a = new Complex(6.6, 12.9);
+        Complex b = new Complex(13.1, 13.5);
+    	System.out.println(a.magnitude());
+    	System.out.println(b.argument());
+        Complex c = a.add(b);
+        System.out.println(c.toString());
+        
     }
 }

src/Complex.java

@@ -29,23 +29,28 @@ public class Complex {
 
   public double magnitude()
   {
-    return 1.0;
+	 double x = this.real;
+     double y = this.imag;
+     return Math.hypot(x, y);
   }
 
   public double argument()
   {
-    return 1.0;
+	  return Math.atan2(imag,real);
   }
 
-  public String toString()
-  {
-    return "";
+  public String toString() {
+      if (imag == 0) return real + "";
+      if (real == 0) return "j"+imag ;
+      if (imag <  0) return real + " - " + "j"+(-imag);
+      return real + " + " + "j"+imag;
   }
 
   public Complex add(Complex complexNum)
   {
     Complex answer = new Complex(0.0,0.0);
-
+    answer.real=this.real+complexNum.real;
+    answer.imag=this.imag+complexNum.imag;
     return answer;
   }