Consider the following premises. t <-> q_8. u -> t. u. Can we infer q_8 from them? If possible, name the inference rules being used at each step.
 From t <-> q_8 we can infer t -> q_8 via biconditional elimination. From u -> t, t -> q_8 we can infer u -> q_8 via transitivity. Finally, from u -> q_8, u we can infer q_8 via modus ponens. Therefore, the answer is yes.