your close!
rearrange and subtitute in -3
(qx + ry + pz) + (rx + py + qz) - 3 = x + y + z
Oops I realized the next step is wrong! The problem may be harder than I thought!
-3 ( x + y + z) + (-3) (x + y + z) - 3 = x + y + z (undistribute p + q + r because they = -3)
-3x - 3y - 3z -3x - 3y - 3z - 3 = x + y + z
-6x - 6y - 6z - 3 = x + y + z
7x + 7y + 7z = 3
answer is 3/7
I think so