Consider the following premises. t_4 <-> u. ~w_1. p_12 or ~t_4. w_1 <-> p_12. Can we infer u from them?
 From p_12 or ~t_4 we can infer t_4 -> p_12. From w_1 <-> p_12, ~w_1 we can infer ~p_12. From t_4 -> p_12, ~p_12 we can infer ~t_4. Finally, from t_4 <-> u, ~t_4 we can infer ~u, which contradicts u. Therefore, the answer is no.