Código HTML:
<script language="javascript"> function sumar() { var suma = 0; suma += parseInt(valuechecked(form.vv)); suma += parseInt(valuechecked(form.co)); var ml = parseInt(document.getElementById("pax").value); if(ml > 25){ document.getElementById('algo').innerHTML = (ml)+10; } else{ document.getElementById('algo').innerHTML = (ml); } } </script>