Consider the following premises. p_6 <-> q_6. p_6 -> q_6. ~q_6. Can we infer ~p_6 from them?
 From p_6 <-> q_6 we can infer q_6 -> p_6. From q_6 -> p_6, p_6 -> q_6 we can infer q_6 <-> p_6. Finally, from q_6 <-> p_6, ~q_6 we can infer ~p_6. Therefore, the answer is yes.