Consider the following premises. s_1 <-> r_3. r_3 <-> q_9. s_1 or q. ~q_9. Can we infer q from them? If possible, name the inference rules being used at each step.
 From r_3 <-> q_9, ~q_9 we can infer ~r_3 via biconditional elimination. From s_1 <-> r_3, ~r_3 we can infer ~s_1 via biconditional elimination. Finally, from s_1 or q, ~s_1 we can infer q via disjunctive syllogism. Therefore, the answer is yes.