Consider the following premises. For all x_7, x_7 will write a letter if and only if x_7 will make tea. For all x_7, x_7 will write a letter or x_7 is a server. There is at least one x_7 for which x_7 will make tea or x_7 is not a server. Can we infer the following from them? For all x_7, x_7 will not make tea.
 From the fact that there is at least one x_7 for which x_7 will make tea or x_7 is not a server we can infer that there is at least one x_7 for which if x_7 were a server, then x_7 is making tea. From the fact that for all x_7, x_7 will write a letter if and only if x_7 will make tea we can infer that for all x_7, if x_7 writes a letter, then x_7 is making tea. Finally, from the fact that for all x_7, if x_7 writes a letter, then x_7 is making tea, that there is at least one x_7 for which if x_7 were a server, then x_7 is making tea, and that for all x_7, x_7 will write a letter or x_7 is a server we can infer that there is at least one x_7 for which x_7 will make tea, which contradicts that For all x_7, x_7 will not make tea. Therefore, the answer is no.