Consider the following premises. For all x_12, x_12 is a janitor if and only if x_12 is an artist. If Barbara cooks, then Jessica is an artist. If Jessica were a janitor, then Barbara is cooking. Can we infer the following from them? If we can, name the inference rule being used: Jessica is a janitor if and only if Jessica is an artist.
We can infer this via the universal instantiation rule. Therefore, the answer is yes.