help on using maxima to solve systems of equations

Hi Tom,

welcome to maxima and thanks for posting a minimal example, that makes
it much easier to answer.

> I'm new to using Maxima. I tried to use the program to solve systems of 
> equations, but I'm not succesful.
> I've reduced my problem to a very simple example:
> 
> (%i1) e1:y=a*x+b;
> (%o1) y=a*x+b
> (%i2) e2:a=c;
> (%o2) a=c
> (%i3) solve(e1,a);
> (%o3) [a=(y-b)/x]
> (%i4) solve([e1,e2],a);
> Inconsistent equations:  [1]
>  -- an error.  To debug this try debugmode(true);

Maxima treats any symbol not mentioned as variable as arbitrary parameter.
It finds out that [e1, e2] is not consistent for arbitrary values
of b, c, x, y. Any of them is determined by the three others so just
pick one as additional variable. For example:

(%i10) solve([e1,e2],[a,c]);
(%o10) [[a = (y-b)/x,c = (y-b)/x]]

HTH,
Harald