How to select an image within 'b' div after hovering over 'a' div?

Bumped into many examples but couldn't get it to work.

echo '<div id="portalcontent">';
   echo '<a href="/post.php?id='.$postid.'" title="Read More" >';
   echo '<div id="featured">';
   echo '<img src="/media.php?id=' . $postid . '" alt="' . $posttitle . '" title="Read More" />';
   echo '</div>';
echo '</a></div>';

I have tried the following so far:

#portalcontent a:hover > #featured img
#portalcontent a:hover > img
#portalcontent a:hover + #featured img
#portalcontent a:hover + img

I currently have:

echo '<div id="portalcontent">';
   echo '<a href="/post.php?id='.$postid.'" title="Read More" >';
      echo '<img src="/media.php?id=' . $postid . '" alt="' . $posttitle . '" title="Read More" />';

#portalcontent a:hover >  img { }

This only seems to work when I hover over the image, not the div.