Variable order and incomplete equations : The variables are defined in the reading order.
Thus the system :
2x + 3z = 4
5x + 6y + 7z = 8
is understood as
Variable y being defined after variable z.
If the wanted order is important, fully define the 1st equation with explicit null coefficients :
2x + 0y + 3z = 4
All variables must be in the 1st member, the second being constant.
No constant terms in the 1st member (silently ignored).
Parameters : The free parameters in the solutions are choosen among the free names in following order :
k m n p q i j r s t u v a b c d e f g h w x y z o l
There is no fixed limit, but don't try more than about 10 equations or unknowns.