Consider the following premises. For all x_9, x_9 will play tennis if and only if x_9 will work. Mary is working. Can we infer the following from them? Mary is playing tennis.
 From the fact that for all x_9, x_9 will play tennis if and only if x_9 will work we can infer that for all x_9, if x_9 works, then x_9 is playing tennis. From the fact that for all x_9, if x_9 works, then x_9 is playing tennis we can infer that if Mary works, then Mary is playing tennis. Finally, from the fact that if Mary works, then Mary is playing tennis, and that Mary is working we can infer that Mary is playing tennis. Therefore, the answer is yes.