Consider the following premises. forall y: Q(y) <-> U(y). Q(a_9) -> U(a_9). Can we infer U(a_9) -> Q(a_9) from them? If possible, name the inference rules being used at each step.
 From forall y: Q(y) <-> U(y) we can infer Q(a_9) <-> U(a_9) via universal instantiation. Finally, from Q(a_9) <-> U(a_9) we can infer U(a_9) -> Q(a_9) via biconditional elimination. Therefore, the answer is yes.