Problem: +(0(),y) -> y +(s(x),y) -> s(+(x,y)) +(x,0()) -> x +(x,s(y)) -> s(+(x,y)) Proof: Church Rosser Transformation Processor (critical pair closing system, Thm 2.11): +(0(),x62) -> x62 +(x63,0()) -> x63 +(x65,s(x64)) -> s(+(x65,x64)) +(s(x67),x66) -> s(+(x67,x66)) critical peaks: joinable Matrix Interpretation Processor: dim=1 interpretation: [+](x0, x1) = 6x0 + 5x1 + 1, [0] = 0, [s](x0) = x0 + 4 orientation: +(0(),x62) = 5x62 + 1 >= x62 = x62 +(x63,0()) = 6x63 + 1 >= x63 = x63 +(x65,s(x64)) = 5x64 + 6x65 + 21 >= 5x64 + 6x65 + 5 = s(+(x65,x64)) +(s(x67),x66) = 5x66 + 6x67 + 25 >= 5x66 + 6x67 + 5 = s(+(x67,x66)) problem: Qed