Consider the following premises. q -> w. u or ~w. u -> q. Can we infer w <-> q from them? If possible, name the inference rules being used at each step.
 From u or ~w we can infer w -> u via rewriting. From w -> u, u -> q we can infer w -> q via transitivity. Finally, from w -> q, q -> w we can infer w <-> q via biconditional introduction. Therefore, the answer is yes.