Perpendicular distance from point to a plane

[PirateFan308]

Homework Statement

Find the perpendicular distance from the point (1,2,3) to the plane x-2y-z=1
One method: find the equation of the line throughout (1,2,3) perpendicular to the plane. Find the intersection of this line and the plane

The Attempt at a Solution

I know the vector (1,-2,-1) is a vector perpendicular to the plane
I'm not sure how to find the distance between where the vector intersects the
plane to the point.

I know what to do if the vector was a line, but I am confused as to how to change the vector into a line.

 

[PirateFan308]

I think the line for the vector (1,-2,-1) that goes through P (1,2,3) is:
x=1+t y=2-2t z=3-t

Is this correct?