Consider the following premises. p_12 <-> r_3. p_8 <-> r_3. ~p_12. Can we infer ~p_8 or t from them?
 From p_12 <-> r_3, ~p_12 we can infer ~r_3. From p_8 <-> r_3, ~r_3 we can infer ~p_8. Finally, from ~p_8 we can infer ~p_8 or t. Therefore, the answer is yes.