Consider the following premises. p_11 <-> q_7. p_11 -> ~s_3. s_3. Can we infer q_7 from them? If possible, name the inference rules being used at each step.
 From p_11 -> ~s_3, s_3 we can infer ~p_11 via modus tollens. Finally, from p_11 <-> q_7, ~p_11 we can infer ~q_7 via biconditional elimination, which contradicts q_7. Therefore, the answer is no.