In a survey of 63 people, 23 people subscribed to magazine A, 21 people subscribed to magazine B, and 17 subscribed to magazine C. For any two of the magazaines, 4 people subscribed to both magazines but not to the thrid magazine. If 5 people in the survey did not subscribe to any of three magazines, how many people subscribed to all three magazines?
这个题目该怎么做啊,怎么我一直做都是负数呢?
可是题目答案是9耶,我都怀疑是不是题目打错了,它选项只有9,7,5,2,
追答第二行打错了,是23+21+17=61
按这个算下去
第四行换成61-8=53
3x+54-x=53
这么算来哥们你是对的···是负数···