Pendant Cutting dimension  square or rectangular piece of cloth. I want to cut three pendants out of the cloth. For mounting, at the wide end of the pendent, I cut it square to facilitate mounting, so the wide end of the pendent is wider than A. I can accurately measure the width (2 * A) and length (L) of the cloth. I accurately know (B). How do I calculate C? Thanks!

I assume that if you extend the lines that intersect the $L$ edge you get isosceles triangles. Lets call the horizontal part of this $X$. Then you have similar triangles, where you can write $$\frac{X}{B}=\frac{X+C}{L}$$ You also have that $$X+C=\frac{A+X}{2}$$ These form a system with two linear equations with two unknowns, $X$ and $C$, which should be easy to solve.