Watch this:

Example

i1*r1+i3*r3-u1=0
i2*r2+i3+r3+u2=0

The unknown varibles are i1, i2, i3.

Does anyone know how to make a procedure which
calculates the unknown varibles.

If it's possible the program should give an output
of its calculation progress. - Step to step.

Any suggestions?

thx, vbzero