Consider the following premises. For all x, x will write a letter. For all x, x is a server if and only if x will write a letter. Can we infer the following from them? For all x, x is a server or x is a taxi driver.
 From the fact that for all x, x is a server if and only if x will write a letter we can infer that for all x, if x writes a letter, then x is a server. From the fact that for all x, if x writes a letter, then x is a server, and that for all x, x will write a letter we can infer that for all x, x is a server. Finally, from the fact that for all x, x is a server we can infer that for all x, x is a server or x is a taxi driver. Therefore, the answer is yes.