418.each of 90 students are at least paticipate at one activities such as 100-meter run... 20 ppl in XX, 40 ppl in JJ, 80
ppl in GG, if 5 ppl join in all three of them, then how many students join in only two of those activities A. 25 B, 15 C. 10 D. 5 E && 答案:55,X+J+G-XJ-XG-JG+XJG=20+40+80-(XJ+XG+JG)+5=90