Consider the following premises. For all x_9, if x_9 takes a plane, then x_9 is playing squash. For all x_9, if x_9 plays squash, then x_9 is taking a plane. There is at least one x_9 for which x_9 is not a mechanic. For all x_9, x_9 is a mechanic if and only if x_9 will play squash. Can we infer the following from them? For all x_9, x_9 is a mechanic if and only if x_9 will play squash.
That is one of the premises. Therefore, the answer is yes.