Consider the following premises. It is sunny if and only if it is cold. It is sunny. If John were a janitor, then it is cold. Can we infer the following from them? If we can, name the inference rule being used: It is cold.
 From the fact that it is sunny if and only if it is cold we can infer that if it is sunny, then it is cold via biconditional elimination. From the fact that it is sunny we can infer that it is sunny or John is a janitor via addition. Finally, from the fact that if it is sunny, then it is cold, that if John were a janitor, then it is cold, and that it is sunny or John is a janitor we can infer that it is cold via disjunction elimination. Therefore, the answer is yes.