YES

1 decompositions
 #1 -----------
   1: F(c(x1)) -> G(x1)
   2: G(x2) -> F(x2)
   3: c(x3) -> x3

@Knuth and Bendix' criterion
--- R
   1: F(c(x1)) -> G(x1)
   2: G(x2) -> F(x2)
   3: c(x3) -> x3

--- S
   1: F(c(x1)) -> G(x1)
   2: G(x2) -> F(x2)
   3: c(x3) -> x3