If you find a solution to these equations, you will find an equation of your line. Please notice that (a,b,c) defines the same line as (ka,kb,kc) and for any non-zero k, and a=b=c=0 defines no line equation at all. Now you can take a=1 and solve for b and c, or take b=1 and solve for a and c, or take c=1 and solve for a and b, at least one of these will work.
