Consider the following premises. s <-> t_2. p -> t_2. ~s. Can we infer p from them? If possible, name the inference rules being used at each step.
 From s <-> t_2, ~s we can infer ~t_2 via biconditional elimination. Finally, from p -> t_2, ~t_2 we can infer ~p via modus tollens, which contradicts p. Therefore, the answer is no.