Consider the following premises. S_8(a_8) -> s_3. s_3 <-> R_8(a_8). forall x_8: R_8(x_8) or S_8(x_8). Can we infer s_3 from them? If possible, name the inference rules being used at each step.
 From forall x_8: R_8(x_8) or S_8(x_8) we can infer R_8(a_8) or S_8(a_8) via universal instantiation. From s_3 <-> R_8(a_8) we can infer R_8(a_8) -> s_3 via biconditional elimination. Finally, from R_8(a_8) -> s_3, S_8(a_8) -> s_3, R_8(a_8) or S_8(a_8) we can infer s_3 via disjunction elimination. Therefore, the answer is yes.