Consider the following premises. p_1 <-> S_20(a_20). q_2 -> R_20(a_20). forall x_20: R_20(x_20) -> S_20(x_20). p_1 -> q_2. Can we infer R_20(a_20) <-> S_20(a_20) from them? If possible, name the inference rules being used at each step.
 From forall x_20: R_20(x_20) -> S_20(x_20) we can infer R_20(a_20) -> S_20(a_20) via universal instantiation. From p_1 -> q_2, q_2 -> R_20(a_20) we can infer p_1 -> R_20(a_20) via transitivity. From p_1 <-> S_20(a_20) we can infer S_20(a_20) -> p_1 via biconditional elimination. From S_20(a_20) -> p_1, p_1 -> R_20(a_20) we can infer S_20(a_20) -> R_20(a_20) via transitivity. Finally, from R_20(a_20) -> S_20(a_20), S_20(a_20) -> R_20(a_20) we can infer R_20(a_20) <-> S_20(a_20) via biconditional introduction. Therefore, the answer is yes.