NO

Problem:
 +(0(),x) -> x
 +(-(x),x) -> 0()
 +(+(x,y),z) -> +(x,+(y,z))
 +(x,y) -> +(y,x)
 -(0()) -> 0()
 -(-(x)) -> x
 -(+(x,y)) -> +(-(x),-(y))

Proof:
 Containment Processor: loop length: 1
                        terms:
                         +(x,y)
                        context: []
                        substitution:
                         x -> y
                         y -> x
  Qed