Consider the following premises. q_3 <-> t_4. q_3 <-> q. ~t_4. Can we infer q from them? If possible, name the inference rules being used at each step.
 From q_3 <-> t_4, ~t_4 we can infer ~q_3 via biconditional elimination. Finally, from q_3 <-> q, ~q_3 we can infer ~q via biconditional elimination, which contradicts q. Therefore, the answer is no.