求问一道prep的题

Lavinia13

A certain one-day seminar consisted of a morning session and an afternoon session. If each of the 126 people attending the seminar attended at least one of the two sessions, how many of the people attended the morning session only?
1) 3/4 of the people attended both sessions
2) 7/8 of the people attended the afternoon session

这道题是刚刚在官方prep软件上做到的
答案是B， 但我觉得应该要两个条件一起才可以吧
求解

Lavinia13

Claire951120 发表于 2017-8-19 16:49
我觉得7/8的人参加下午的session是既包括了只参加下午session的也包括了两个都参加的。所以剩下1/8就是只参 ...

哦哦对的 谢谢啦！