1. After her opponent had spent several weeks slandering her, the candidate decided to fight fire with fire.2. When evangelists come to our house and try to convert us, my mother would do the same thing to them and try to convert them to her religion.
 do the same thing to somebody fight fire with firefight fire with fire 的意思是 "以其人之道還之其人之身"。
All the work I've been putting into this project has been all for nothng because my boss is shutting it down.