How to calculate (ax+by+cz=0) this type of equation in c++?

How to calculate (ax+by+cz=0) this type of equation in c++?

Consider these three equation
a1x+b1y+c1z=0
a2x+b2y+c2z=0
a3x+b3y+c3z=0
a1,a2,a3,b1,b2,b3,c1,c2,c3 are given
Now what is x,y,z?
I want to code it in c++ and need logic. Some one told me about iterative
method but i can't understand what is iterative method.
Can anyone help me, please.