Consider the following premises. P_20(a_20) -> w. r_1. forall x_20: P_20(x_20). Can we infer w from them? If possible, name the inference rules being used at each step.
 From forall x_20: P_20(x_20) we can infer P_20(a_20) via universal instantiation. From P_20(a_20), r_1 we can infer P_20(a_20) and r_1 via conjunction. From P_20(a_20) and r_1 we can infer P_20(a_20) via simplification. Finally, from P_20(a_20) -> w, P_20(a_20) we can infer w via modus ponens. Therefore, the answer is yes.