#intro-img div + selector doesn't work.

I'm getting super frustrated by something I can not work out to get to work.

Doing the responsive web design section and am at the point where we're removing items below 480px resolution.

Asked to use a div id and selector to remove an image from the div below 480px, and I can not get it to work.

I thought I was been thick, maybe I still am.

I can remove the image if I give the image the class of noShow and change the CSS to .noShow { display: none; } but if I use the code #intro-img or #intro img { display: none; } the image stays put.

However, if I use the code #intro { display: none; } the intro text goes away but the image remains.

The selector just doesn't select the img.

I've tried using sublime text 2 instead of my preferred dreamweaver in case it was a quirk of dreamweaver but no joy.

Searching the forums my code is identical as is the code from the video. I downloaded and checked the project files css but that code hides the text and keeps the image which I can do.

Anyone have any ideas? I can upload to codepen if that helps.

Would really really appreciate some light being shed on this as it is infuriating.

Thanks.