The given plane has normal vector

Scaling n by a real number t gives a set of vectors that span an entire line through the origin. Translating this line by adding the vector <2, 1, 1> makes it so that this line passes through the point (2, 1, 1). So this line has equation

This line passes through (2, 1, 1) when t = 0, and the line intersects with the plane when

which corresponds the point (3, -1, 1) (simply plug t = 1 into the coordinates of
).
So the distance between the plane and the point is the distance between the points (2, 1, 1) and (3, -1, 1):
