Does this help you to understand simulataneous equations? It seems you say that you can solve algebraically, but I can't see that you have done that. Would it not be better to learn how to solve simultaneous equations? The equation is solved. I don't see the point of using the classpad to mimic elimination and substitution method, two methods that are quicker on paper than via a classpad. This is probably the most read and commented on articles I have written because it addresses an issue of teachers (yes us!) not utilising CAS to reduce computational load. For a student to reach the point of knowing it is a simultaneous equation question can require a lot of work (see linear programming for instance), to be able to solve quickly (a year 8/9 task under national curriculum) is something worthwhile for those students that find solving trivial and tedious. Matrices is a 3CD MAS topic, something that I haven't taught yet. If you are interested in looking into this further, I'd suggest the excellent http://www.classpad.com.au Their tutorials are excellent on a wide range of topics (and free!).