prep 数学ds关于集合的一题，晕晕了。

carolcai

10.  719-!-item-!-187;#058&000515

Of the 800 students at a certain college, 250 students live on campus and are more than 20 years old.  How many of the

 

800 students live on campus and are 20 years old or less?

 

(1)  640 students at the college are more than 20 years old.

 

(2)  60 students at the college are 20 years old or less and live off campus.

答案是C，我都给整晕了，感觉题目绕绕的啊。能给指条明路吗？

carolcai

prep破解版我上传了，你下下吧