Consider the following premises. s_1 -> t. ~q_18. t <-> q_18. s_1 or w. Can we infer w or q from them? If possible, name the inference rules being used at each step.
 From t <-> q_18, ~q_18 we can infer ~t via biconditional elimination. From s_1 -> t, ~t we can infer ~s_1 via modus tollens. From s_1 or w, ~s_1 we can infer w via disjunctive syllogism. Finally, from w we can infer w or q via addition. Therefore, the answer is yes.