Consider the following premises. ~s_2. s_2 or ~q. q or ~s_2. Can we infer q from them? If possible, name the inference rules being used at each step.
 From s_2 or ~q we can infer q -> s_2 via rewriting. From q or ~s_2 we can infer s_2 -> q via rewriting. From q -> s_2, s_2 -> q we can infer q <-> s_2 via biconditional introduction. Finally, from q <-> s_2, ~s_2 we can infer ~q via biconditional elimination, which contradicts q. Therefore, the answer is no.