[CVALE] GIMP Help

[Terry]

I'm looking for assistance with what I would guess is a simple task in GIMP. (I only use GIMP about 
once a year).

Currently in GIMP I have the following 3 layers.  All layers have a transparent backgound.

- a blank transparent "Background"
- a black filled triangle
- the letter 'C' in white positioned correctly (over the triangle)

How do I "cut" out the letter 'C' in the black triangle so that the transparent background fills the 
space where the 'C' would be?

That is, the finished graphic (GIF file) could be placed on a web page having a blue background and 
the graphic would look like a black triangle with a blue (background) 'C' in the middle.

Note that in reality the black triangle is a large complicated shape that took me a long time to 
make and there is a lot of carefully placed text involved.  So I'm hoping the solution doesn't 
involve recreating the shape or text layers.

I'm using version 2.2.10 of GIMP.

I've spent a couple hours with this "simple" task and haven't figured out how to use masks and 
channels properly.

Thanks.

Terry Montgomery

P.S. Anyone bringing a "show-and-tell" or presentation to the CVALE meeting on Tuesday?