I have two lines $(5,5,4) (10,10,6)$ and $(5,5,5) (10,10,3)$ with same $x$, $y$ and difference in $z$ values.

Please some body tell me how can I find the intersection of these lines.

By using answer given by coffemath i would able to fint the intersection point for above given points. But getting problem for $(6,8,4) (12,15,4)$ and $(6,8,2) (12,15,6)$. Unable calculate common point for these points as it resulting Zero. Any Ideas to resolve this.

Thanks, Kumar.