YES Problem: +(-(x,y),z) -> -(+(x,z),y) -(+(x,y),y) -> x Proof: Matrix Interpretation Processor: dim=3 interpretation: [1 1 1] [1 0 0] [1] [+](x0, x1) = [0 0 1]x0 + [0 0 0]x1 + [0] [0 1 0] [0 0 0] [1], [1 0 0] [1 0 0] [0] [-](x0, x1) = [0 0 1]x0 + [1 0 0]x1 + [0] [0 1 0] [1 0 0] [1] orientation: [1 1 1] [3 0 0] [1 0 0] [2] [1 1 1] [1 0 0] [1 0 0] [1] +(-(x,y),z) = [0 1 0]x + [1 0 0]y + [0 0 0]z + [1] >= [0 1 0]x + [1 0 0]y + [0 0 0]z + [1] = -(+(x,z),y) [0 0 1] [1 0 0] [0 0 0] [1] [0 0 1] [1 0 0] [0 0 0] [1] [1 1 1] [2 0 0] [1] -(+(x,y),y) = [0 1 0]x + [1 0 0]y + [1] >= x = x [0 0 1] [1 0 0] [1] problem: Qed