GWD数学题 过几天就要考试了 求大家解答 谢谢谢谢了

joanna5200

On a company-sponsored cruise, of the passengers were company employees and the remaining passengers were their guests. If of the company-employee passengers were managers, what was the number of company-employee passengers who were NOT managers?

(1)There were 690 passengers on the cruise.

(2)There were 230 passengers who were guests of the company employees.
正确答案是D  条件二 怎么也想不明白为啥也可以单独成立呢？？求牛牛解答 谢谢谢谢了