Consider the following premises. For all x, if x takes a plane, then x is a taxi driver. For all x, x is a taxi driver if and only if x will play a game. For all x, x will take a plane if and only if x will play a game. Can we infer the following from them? If we can, name the inference rule being used: For all x, if x were a taxi driver, then x is taking a plane.
 From the fact that for all x, x is a taxi driver if and only if x will play a game we can infer that for all x, if x were a taxi driver, then x is playing a game via universal biconditional elimination. From the fact that for all x, x will take a plane if and only if x will play a game we can infer that for all x, if x plays a game, then x is taking a plane via universal biconditional elimination. Finally, from the fact that for all x, if x were a taxi driver, then x is playing a game, and that for all x, if x plays a game, then x is taking a plane we can infer that for all x, if x were a taxi driver, then x is taking a plane via universal transitivity. Therefore, the answer is yes.