Many thanks for this.  I have implemented all of your comments except the first.  I ahve altered the explanation about 'values of solutions' to make it, I hope, clearer just what I mean.  I have managed to alter the diagrams as you suggest using Inkscape which I downloaded a few days ago.  I would welcome your help pages about this, as my first attempts at creating diagrams were unsuccessful - all the lines, text etc whihc I created came out in light grey rather than black even though I set it at black using the fill, so either I am doing something very stupid, or there is some setting which I am missing.

I am now going to make the page live.

Thanks again