YES

Problem:
 f(f(a(),f(x,a())),a()) -> f(a(),f(f(x,a()),a()))

Proof:
 DP Processor:
  DPs:
   f#(f(a(),f(x,a())),a()) -> f#(f(x,a()),a())
   f#(f(a(),f(x,a())),a()) -> f#(a(),f(f(x,a()),a()))
  TRS:
   f(f(a(),f(x,a())),a()) -> f(a(),f(f(x,a()),a()))
  EDG Processor:
   DPs:
    f#(f(a(),f(x,a())),a()) -> f#(f(x,a()),a())
    f#(f(a(),f(x,a())),a()) -> f#(a(),f(f(x,a()),a()))
   TRS:
    f(f(a(),f(x,a())),a()) -> f(a(),f(f(x,a()),a()))
   graph:
    f#(f(a(),f(x,a())),a()) -> f#(f(x,a()),a()) ->
    f#(f(a(),f(x,a())),a()) -> f#(f(x,a()),a())
    f#(f(a(),f(x,a())),a()) -> f#(f(x,a()),a()) ->
    f#(f(a(),f(x,a())),a()) -> f#(a(),f(f(x,a()),a()))
   SCC Processor:
    #sccs: 1
    #rules: 1
    #arcs: 2/4
    DPs:
     f#(f(a(),f(x,a())),a()) -> f#(f(x,a()),a())
    TRS:
     f(f(a(),f(x,a())),a()) -> f(a(),f(f(x,a()),a()))
    KBO Processor:
     argument filtering:
      pi(a) = []
      pi(f) = [0,1]
      pi(f#) = [0,1]
     weight function:
      w0 = 1
      w(f) = w(a) = 1
      w(f#) = 0
     precedence:
      f# ~ f ~ a
     problem:
      DPs:
       
      TRS:
       f(f(a(),f(x,a())),a()) -> f(a(),f(f(x,a()),a()))
     Qed