jquery hide show
HTML
<select id="prefix-nums">
<option value="default">Default</option>
<option value="first">first</option>
<option value="other">other</option>
</select>
<div id="prefix-text-1">
I'll hide when you select other
</div>
JavaScript
$('#prefix-nums').on('change', function(e) {
if ($(this).val() == 'other') {
$('#prefix-text-1').show();
$("#prefix-text-1").css({
display: "inline-block"
});
} else if ($(this).val() == 'first') {
$('#prefix-text-1').hide();
}
});