MAYBE
Time: 0.020

Problem:
 Equations:
  
 TRS:
  app(nil(),k) -> k
  app(l,nil()) -> l
  app(cons(x,l),k) -> cons(x,app(l,k))
  sum(cons(x,nil())) -> cons(x,nil())
  sum(cons(x,cons(y,l))) -> sum(cons(plusAC(x,y),l))
  sum(app(l,cons(x,cons(y,k)))) -> sum(app(l,sum(cons(x,cons(y,k)))))
  sum(cons(0(),cons(plusAC(x,y),l))) -> pred(sum(cons(s(x),cons(y,l))))
  plusAC(0(),y) -> y
  plusAC(s(x),y) -> s(plusAC(x,y))
  pred(cons(s(x),nil())) -> cons(x,nil())

Proof:
 Open