Can't you find values of x, y and z that satisfy the equation (those values give you the coordinates of points in the plane)? eg. If x = 1 and y = 1 then it follows that z = 0. So (1, 1, 0) is a point in the plane. Call it P. etc.

Once you have three points P, Q and R, you should have been taught how to find vectors PQ and PR. Go back to your class notes and review that material.

If you need more help, please show all your work and say where you get stuck.