Maths nerds, lend me your helps!

Working in three dimensions and cartesion co-ords, I've got a heap of lines and a heap of planes, and I need to know the point at which a given line intersects a given plane. I want to set up a spreadsheet where I just put it three points from the plane, and two points from the line, and it spits out the intersection point (assuming there's a unique solution).

I found this:

http://en.wikipedia.org/wiki/Line-plane_intersection, and was using the algebraic method at the bottom, and it was going great, right up to here:

d = ((p

_{o}-l

_{o}).n)/(l.n)

Which gives me this:

d = ||19.65| |16.9|| | 1.000|

||15.35| - |12.1|| * | 1.000|

|| 9.15| | 8.6|| |-2.382|

-----------------------------

| 0 | | 1.000|

| 0 | * | 1.000|

| 1 | |-2.382|

How on earth do I solve that to end up with a scalar quantity?