YES
Time: 0.013

Problem:
 Equations:
  fAC(fAC(x1,x2),x3) -> fAC(x1,fAC(x2,x3))
  fAC(x1,x2) -> fAC(x2,x1)
  fAC(x1,fAC(x2,x3)) -> fAC(fAC(x1,x2),x3)
  fAC(x2,x1) -> fAC(x1,x2)
 TRS:
  fAC(g(g(x)),x) -> fAC(g(x),g(x))
  fAC(fAC(x,x),g(x)) -> fAC(x,h(x))

Proof:
 AC-RPO Processor:
  precedence:
   g > fAC > h
  status:
   
  problem:
   Equations:
    fAC(fAC(x1,x2),x3) -> fAC(x1,fAC(x2,x3))
    fAC(x1,x2) -> fAC(x2,x1)
    fAC(x1,fAC(x2,x3)) -> fAC(fAC(x1,x2),x3)
    fAC(x2,x1) -> fAC(x1,x2)
   TRS:
    
  Qed