rusVolk,
<!DOCTYPE HTML>
<html>
<head>
<title>Untitled</title>
<meta charset="utf-8">
<style type="text/css">
#show{
color: #FF00FF;
font-size: 48px;
}
</style>
</head>
<body>
<a href="">Основы html<span class="mli" id="adm">20</span></a>
<a href="">Java Script<span class="mli" id="bfg">11</span></a>
<div id="show"></div>
<script>
var otv = 0,
mmm = document.getElementById("adm"),
sss = document.getElementById("bfg"),
div = document.getElementById("show");
mmm = mmm.innerHTML;
sss = sss.innerHTML;
mmm = +mmm;
sss = +sss;
otv = mmm + sss;
div.innerHTML = otv;
</script>
</body>
</html>