请教prep貌似简单but吐血题目（1楼增加DS一题）

85.   9649-!-item-!-187;#058&007038

Of the 800 employees of Company X, 70 percent have been with the company for at least ten years.  If y of these "long-term" members were to retire and no other employee changes were to occur, what value of y would reduce the percent of "long-term" employees in the company to 60 percent?

(A) 200

(B)  160

(C)  112

(D)  80

(E)  56

为什么答案会是200？ 我选了80，怎么算都算不出，是不是我什么概念没搞清楚？

If x and y are positive integers such that x = 8y + 12, what is the greatest common divisor of x and y ?

(1) x = 12u, where u is an integer.

(2) y = 12z, where z is an integer.

请问B怎么推出xy 的最大公约数呢？

请问B怎么推出xy 的最大公约数呢？

请问B怎么推出xy 的最大公约数呢？

我只会把 12 24 36代进去看，请问怎么正常解题？

我只会把 12 24 36代进去看，请问怎么正常解题？

我只会把 12 24 36代进去看，请问怎么正常解题？

还有一题在破解版里找不到，讲一个人炒股，好像就买了俩股，都是96刀，然后他把股卖了，一个赚了20%，一个赔了20%，问他总的来说赚了还是赔了？

我选没赚也没赔，答案是赔了8刀

...吐血中...

阿...一言惊醒梦中人...谢谢~

(560-y)/(800-y)=0.6

y=200

汗，脑袋在这个时候开始打结

又看了一眼，你说对了

谢谢大家

...晕

恩，没错，这个总结好。

我也正在吐血.....

80.   7589-!-item-!-187;#058&005492

If x and y are positive integers such that x = 8y + 12, what is the greatest common divisor of x and y ?

(1) x = 12u, where u is an integer.

(2) y = 12z, where z is an integer.

请问B怎么推出xy 的最大公约数呢？

我只会把 12 24 36代进去看，请问怎么正常解题？