1. His wife cheated on him; that’s why they got divorced.2. She was having an affair with a married man.
 cheat on somebody have an affair這是最普遍的說法.
他太太有外遇, 所以他們才離婚. 她與有婦之夫外遇.
All the wrk I've been putting into this project has been all for nothing because my boss is shutting it down.