Consider the following premises. p_6 or t_3. ~p_6. s -> q_12. s. Can we infer ~t_3 from them? If possible, name the inference rules being used at each step.
 From s -> q_12, s we can infer q_12 via modus ponens. Finally, from p_6 or t_3, ~p_6 we can infer t_3 via disjunctive syllogism, which contradicts ~t_3. Therefore, the answer is no.