4-4= ?四减四等于几One day, the teacher inquired Peter: How much is four minus four ? Peter was tongue-tied.一天，老师问彼得：“4减4等于几？”彼得张口结舌答不上来。The teacher got angry and said: What a footl You S8e if I put four coins in your pocket, but there is a hole in your pocket and all of them leak out,now what is left in your pocket?老师生气地说：“真笨！比如我给你衣袋里装进4个硬币，可你衣袋上有个窟窿，硬币全从这里漏掉了，那么，你衣袋里还剩下什么？”The hole. replied Peter.“还剩下个窟窿。”彼得答道。
