求助 og12 ds 50

samuelxie

how many people are directors of both company k and comany r?

(1)  there were 17 directors pesent at a joint meeting of the directors of company k and company r , and no directors were absent

(2) company k has 12 directors and company  r has 8 directors

这题我估计是我的翻译有问题，看不懂为什么选c，请讲解一下

samuelxie

i got it，thx！

handapink

条件1说明K并R有17人。
条件2说明集合K有12人，R有8人。
现求K交R有多少人。。。。
画下图显然是C