Do you know a program that can solve equatation by given variable? And where I can tell the program which variables are parameters?

possible duplicate of Software to write and manipulate mathematical equations – sblair May 28 '11 at 13:20

2Have you tried Wolfram Alpha? – sblair May 28 '11 at 13:22

But something offline more mathematical with indexes etc. – oneat May 28 '11 at 13:41

You keep deleting your comments before anyone has a chance to respond to them. If the possible duplicate does not help with your problem, then please edit your question to be more specific. Some examples might help too. – sblair May 28 '11 at 14:09

I need a program which could from: xa/b=5a give me x=5b (where b is param for programming use), but the equatations will be more complicated and sometimes Simultaneous. – oneat May 28 '11 at 21:56
take a look at this: http://www.sagemath.org/doc/tutorial/tour_algebra.html
other possibilities which come to my mind:
commercial:
free:

2
You could use WolframAlpha online (does an excellent job) or use Microsoft Mathematics (simply amazing). The best thing about Microsoft Mathematics is that, for many problems, it shows you the steps it took to solve the equation. They used to charge for Microsoft Mathematics, but it looks like it is free now.