Answer:
B
Explanation:
What you're seeing is a (x,y,z) plane.
At this point, it's just plug and play.
Looking at choice B....
(1) + (2) + (2)(3) = 1 + 2 + 6 which is indeed 9
(2)(1) + (2)(2) + 3(3) = 2 + 4 + 9 which is indeed 15
(1) + (-3) = 1 - 3 which is indeed -2