[Gimp-user] How to replace foreground with background pixels

[rhimbo <forums gimpusers com>]

Hello all,

I've tried watching some YouTube tutorials to figure out my problem, and I've
also done some searching but can't quite figure out how to accomplish my goal. 
I'm a novice still and part of my problem is that I'm not well-versed in
graphics concepts, so I think I'm not comprehending some of the explanations.

I have several images which are just screen grabs or PDFs.  For example, the one
attached is from a PDF which contains annotations (red rectangle).  I can import
the PDF as a JPEG, that's no problem.

I'm trying to remove the red rectangle and in its place just have the
"background" that was there before the red rectangle was added.

If someone could just point me in the right direction... a tutorial, part of the
user's guide, whatever, I'm happy to go dive in.

Some of the YouTube tutorials showed adding layers, turning the image to gray
scale or black-and-white, reversing foreground and background, etc.  My head was
spinning.  They went kinda fast for a novie.

One of these days I'm going to start from the very beginning and learn this
great tool from the perspective of concepts and formal immersion into the
graphics world.

Many thanks in advance...

Attachments:
* https://www.gimpusers.com/system/attachments/1306/original/Screen_Shot_2019-11-30_at_12.01.51_PM.png

-- 
rhimbo (via www.gimpusers.com/forums)