Consider the following premises. For all z, z will write a letter if and only if z will play a game. For all z, z will not write a letter. Karen is playing a game if and only if it is windy. Can we infer the following from them? If we can, name the inference rule being used: It is not windy.
 From the fact that for all z, z will write a letter if and only if z will play a game, and that for all z, z will not write a letter we can infer that for all z, z will not play a game via universal biconditional elimination. From the fact that for all z, z will not play a game we can infer that Karen is not playing a game via universal instantiation. Finally, from the fact that Karen is playing a game if and only if it is windy, and that Karen is not playing a game we can infer that it is not windy via biconditional elimination. Therefore, the answer is yes.