Consider the following premises. Charles is writing a letter or Thomas is not drinking water. Charles is bored or Thomas is drinking water. For all x_13, x_13 is bored if and only if x_13 will write a letter. Can we infer the following from them? Charles is not writing a letter.
 From the fact that for all x_13, x_13 is bored if and only if x_13 will write a letter we can infer that for all x_13, if x_13 were bored, then x_13 is writing a letter. From the fact that for all x_13, if x_13 were bored, then x_13 is writing a letter we can infer that if Charles were bored, then Charles is writing a letter. From the fact that Charles is writing a letter or Thomas is not drinking water we can infer that if Thomas drinks water, then Charles is writing a letter. Finally, from the fact that if Charles were bored, then Charles is writing a letter, that if Thomas drinks water, then Charles is writing a letter, and that Charles is bored or Thomas is drinking water we can infer that Charles is writing a letter, which contradicts that Charles is not writing a letter. Therefore, the answer is no.