How to define an arbitrary constant for equations?

Hello everyone. I want to define a arbitrary constant for equations that I wrote. How can I define? I tried to define with cond command but it didn't work.

v1=6;
v3=18;

syms v2 v4 v5 v6

eqn1= -v4+v5==-v3;
eqn2= -v2+v6==v3;
eqn3= -v5-v6==-v1;

cond= v6~=0;
[v2 v4 v5 v6]=solve(eqn1, eqn2, eqn3);

[v2 v4 v5 v6]

Answer 1

[Birdman]

If you are talking about making an assumption, you can do it as follows:

v1=6;
v3=18;
syms v2 v4 v5 v6
eqn1= -v4+v5==-v3;
eqn2= -v2+v6==v3;
eqn3= -v5-v6==-v1;
assume(v6~=0)
[v2 v4 v5 v6]=solve(eqn1, eqn2, eqn3);
[v2 v4 v5 v6]

[Yunus Emre ERYILMAZ]

That's what I want. Thank you very much.