How can I filter a query by post id?

So you want the values 108,78,90 corresponding to the meta key ‘areas’ for the post with ID 94?

First retrieve those IDs:

$the_post_id = 94;
$area_ids = get_post_meta( $the_post_id, 'areas', false );

//Make sure they're all positive integers
$area_ids = array_map( 'absint', $area_ids );

if( $area_ids ){
   //We have IDs, retrieve posts
   $areas = get_posts( array(
      'post_type' => 'area',
      'numberposts' => -1,
      'post__in' => $area_ids;
   ));

   if( $areas ){
       //We have areas
       foreach( $areas as $area ){
          echo get_the_title( $area ). '<br/>';
       }
   }

}

The above has not been tested, but should work in theory. If you want $the_post_id to the be ID of the post currently being viewed then you can use get_the_ID().