First, fix your markup by closing the input tags. Then:
$(function () {
$('input[type="radio"]').on("change", function () {
var firstChecked = $('input[type="radio"][name="first"]:checked').val();
var secondChecked = $('input[type="radio"][name="second"]:checked').val();
if (typeof firstChecked == "undefined" || typeof secondChecked == "undefined") return;
var result = firstChecked == "yes" && secondChecked == "yes" ? "High" : firstChecked == "no" && secondChecked == "no" ? "Low" : "Medium";
$('.result').text(result);
});
});