jquery finding and add clss to element : How do i add class to the span element.

For instant - class="fa fa-close"

I need to do it with jquert - finding the "sec" by id (i.e: id="sec2") and than by attribute (i.e: data-id="attrac-24")

HTML example

    <div class="well dropZone" id="sec2">
    
    	<div class="panel panel-info attrac ui-widget-content" data-id="attrac-24" >
    		<div class="panel-heading"><?PHP echo mb_substr ($attracIndex['title'], 0, 45, "utf-8") ?> <span class="pull-right"><i class="fa"></i></span></div>
    		<div class="panel-body"><?PHP echo mb_substr ($attracIndex['des'], 0, 120, "utf-8")?></div>
    	</div>									
    
    </div>
    
    <div class="well dropZone" id="sec3">
    
    	<div class="panel panel-info attrac ui-widget-content" data-id="attrac-24" >
    		<div class="panel-heading"><?PHP echo mb_substr ($attracIndex['title'], 0, 45, "utf-8") ?> <span class="pull-right"><i class="fa"></i></span></div>
    		<div class="panel-body"><?PHP echo mb_substr ($attracIndex['des'], 0, 120, "utf-8")?></div>
    	</div>
    
    	<div class="panel panel-info attrac ui-widget-content" data-id="attrac-35" >
    		<div class="panel-heading"><?PHP echo mb_substr ($attracIndex['title'], 0, 45, "utf-8") ?> <span class="pull-right"><i class="fa"></i></span></div>
    		<div class="panel-body"><?PHP echo mb_substr ($attracIndex['des'], 0, 120, "utf-8")?></div>
    	</div>		
    
    </div>

JQUERY

    var secID = event.target.id;
    var attacID = ui.item.data('id');

I  tried this:

    $("#"+secID + " [data-id='"+attacID+"']" ).find("fa").addClass("fa-close");