Consider the following premises. R_13(a_13) <-> w. S_13(a_13) <-> w. forall x_13: R_13(x_13) or S_13(x_13). Can we infer w from them? If possible, name the inference rules being used at each step.
 From forall x_13: R_13(x_13) or S_13(x_13) we can infer R_13(a_13) or S_13(a_13) via universal instantiation. From R_13(a_13) <-> w we can infer R_13(a_13) -> w via biconditional elimination. From S_13(a_13) <-> w we can infer S_13(a_13) -> w via biconditional elimination. Finally, from R_13(a_13) -> w, S_13(a_13) -> w, R_13(a_13) or S_13(a_13) we can infer w via disjunction elimination. Therefore, the answer is yes.