Consider the following premises. forall x: Q(x) <-> U(x). U(f) <-> Q(f). Can we infer Q(f) <-> U(f) from them?
 From forall x: Q(x) <-> U(x) we can infer forall x: U(x) -> Q(x). From forall x: U(x) -> Q(x) we can infer U(f) -> Q(f). From U(f) <-> Q(f) we can infer Q(f) -> U(f). Finally, from Q(f) -> U(f), U(f) -> Q(f) we can infer Q(f) <-> U(f). Therefore, the answer is yes.