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<!DOCTYPE html>
<html>
<head>
<title>JS tutorial</title>
<style type="text/css">
body {
    margin-top:20px;
    background-color:#ffa;
}
</style>
<script type="text/javascript">
    var val1 = 12;
    var val2 = "8";
    var val3 = 8;
    var val4 = NaN;
    document.write("The result of <i>( "+val1+" + "+val2+" )</i> equals: <b><br />" + (val1 + val2) + "</b><br /><br />");
    document.write("The result of <i>( "+val1+" + "+val3+" )</i> equals: <b><br />" + (val1 + val3) + "</b><br /><br />");
    document.write("The result of <i>( "+val1+" - "+val2+" )</i> equals: <b><br />" + (val1 - val2) + "</b><br /><br />");
    document.write("The result of <i>( "+val1+" - "+val4+" )</i> equals: <b><br />" + (val1 - val4) + "</b><br /><br />");
</script>   
</head>
<body>
</body>
</html>