Consider the following premises. For all x, if x were an artist, then x is a musician. For all x, x is a musician if and only if x is an artist. Can we infer the following from them? If we can, name the inference rule being used: For all x, x is an artist if and only if x is a musician.
 From the fact that for all x, x is a musician if and only if x is an artist we can infer that for all x, if x were a musician, then x is an artist via universal biconditional elimination. Finally, from the fact that for all x, if x were an artist, then x is a musician, and that for all x, if x were a musician, then x is an artist we can infer that for all x, x is an artist if and only if x is a musician via universal biconditional introduction. Therefore, the answer is yes.