JS Operators

<html>
<body>
<script type="text/javascript">
   var a = 5 + 5;
   var b = "5" + 5;
   var c = 5 + 5 + "5" + 5
   var d = "Hello" + 5;
   document.write(a + "<br>" + b + "<br>" + c + "</br>" + d);
   document.write("</br>");
   document.write(typeof(a));
   document.write("</br>");
   document.write(typeof(b));
   document.write("</br>");
   document.write(typeof(c));
   document.write("</br>");
   document.write(typeof(d));
</script>
</body>
</html>