Consider the following premises. If Linda were fast, then Susan is a soldier. James is a writer if and only if Linda is fast. Linda is fast if and only if Susan is a soldier. Can we infer the following from them? If James were a writer, then Susan is a soldier.
 From the fact that Linda is fast if and only if Susan is a soldier we can infer that if Susan were a soldier, then Linda is fast. From the fact that James is a writer if and only if Linda is fast we can infer that if James were a writer, then Linda is fast. From the fact that if Linda were fast, then Susan is a soldier, and that if Susan were a soldier, then Linda is fast we can infer that Linda is fast if and only if Susan is a soldier. From the fact that Linda is fast if and only if Susan is a soldier we can infer that if Linda were fast, then Susan is a soldier. Finally, from the fact that if James were a writer, then Linda is fast, and that if Linda were fast, then Susan is a soldier we can infer that if James were a writer, then Susan is a soldier. Therefore, the answer is yes.