Of the 32 students in a certain class, 15 are in a music club and 20 are
in a dance club. If 10 of the students are not in either club, how many of
the students are in only one of the two clubs?
A. 5 B. 9 C.10 D. 17 E. 25
如果設兩個社團都都參加為X
15+20-X+10=32, X=13
請問只參加一個社團的人數的算法用兩者聯集減掉交集
15+20-13=22是哪裡出了問題呢?
謝謝