If P1:r→⋅n→1−d1=0,P2:r→⋅n2→−d2=0 and  P3:r→⋅n3→−d3=0 are three planes n1→,n2→ and n3→ are  three non-coplanar vectors, then three lines P1 =0, P2=0; P2= 0, P3 = 0 and P3 : 0, P1 : 0 are

P1 =0, P2=0; P2= 0, P3 = 0 and P3 : 0, P1 : 0 are  lines of intersection of the three planes P 1 P2 and P3As n1→,n2→ and n3→  are non-coplanar, planes P1, P2 and P3 will intersect at unique point. So the given lines will pass through a fixed point.