Consider the following premises. ~r or s_1. w. s -> t. r or s. s_1 -> t. Can we infer w and t from them? If possible, name the inference rules being used at each step.
 From r or s, ~r or s_1 we can infer s or s_1 via resolution. From s -> t, s_1 -> t, s or s_1 we can infer t via disjunction elimination. Finally, from w, t we can infer w and t via conjunction. Therefore, the answer is yes.