Give the equation of a plane containing the points (1, 0, 0) and (1, 2, 1) and parallel to

Question

the line whose equations are x = y, z =

so i found n to be <0,1,2> then i used the equation n(r-ro) and got y-x+2z.

the answer is x-y+2z =1. how do they get =1 and why is it x-y

thanks!