Given the figure below find the values of x and z

Well, you can actually tell it is D without solving it because it is the only one that has the x value as 3.  But just to be sure.

Plug in 3 for x into the equation:
3(3)-y=9 and solve for y
9-y=9 subtract 9 from both sides
-y=0 so y=0

so the value is (3,0)