Consider the following premises. For all x_7, x_7 will play squash if and only if x_7 will cook. David is cooking or Richard is a writer. David is not playing squash. Can we infer the following from them? Richard is a writer.
 From the fact that for all x_7, x_7 will play squash if and only if x_7 will cook we can infer that David is playing squash if and only if David is cooking. From the fact that David is playing squash if and only if David is cooking, and that David is not playing squash we can infer that David is not cooking. Finally, from the fact that David is cooking or Richard is a writer, and that David is not cooking we can infer that Richard is a writer. Therefore, the answer is yes.