Consider the following premises. p_6 -> s. p_3 <-> q_4. ~s. p_6 <-> q_4. Can we infer p_3 from them?
 From p_6 -> s, ~s we can infer ~p_6. From p_6 <-> q_4, ~p_6 we can infer ~q_4. Finally, from p_3 <-> q_4, ~q_4 we can infer ~p_3, which contradicts p_3. Therefore, the answer is no.