陆旭老师，我有一些做过的assumption题目取非的句子搞不清，你能帮忙看下吗(不说这道题目的解题思路，单纯就是取非问题，特别是双重否定或者从句里面有否定词） 1.No part of a person’s brain that is damaged by a stroke ever recovers.---> some part of a person's brain that is damaged by a stroke ever recovers. 2.Impairment of linguistic capabilities does not occur in people who have not suffered any damage to any language center of the brain.这个句子我不太会取非，正过来说这个句子就是Impairment of linguistic capabilities occurs in people who have suffered any damage to any language center of the brain.那么我取非是Impairment of linguistic capabilities occurs in people who have not suffered any damage to any language center of the brain. 3.If there are language centers on the left side of the brain, any serious stroke affecting that side of the brain damages at least one of them. 取非If there are language centers on the left side of the brain, any serious stroke affecting that side of the brain damages nothing of them. 4.这题出现两个not The collection fee will not significantly affect the purchasing power of most residents, even if their households do not reduce the amount of trash they put out. 我取非直接去前面的not: The collection fee will significantly affect the purchasing power of most residents, even if their households do not reduce the amount of trash they put out. 5.这个也差不多 Not all steel producers were unaffected by country A’s newly imposed tariffs. 我取非All steel producers were unaffected bycountry A’s newly imposed tariffs. 6.There are no plants native to western Africa that, if domesticated, could serve as staple food crops. 这个if domesticated是不是可以不管，直接改成There are some plants native to western Africa that, if domesticated, could serve as staple food crops.

GMAT数学（博智教材）第62页：If X is equal to the sum of the even integers from 40 to 60, inclusive, and y is the number of even integers from 40 to 60, inclusive, what is the value of x+y? X=40+42+44......60=550 Y=(60-40)/2+1=11, 答案应该是561，为什么书后面的答案显示是560？

数学书61页36题，一个男的卖每条7块的领带和每件14元的衬衫。如果他总共卖了10件，110元，求卖了几条领带？ 我得小数，选项里没有。

DS：5个数中 median 小于 average ；另外7个数也median 小于 average，然后这12个数没有重复的，12个数放在一个数集里面，问是不是median 小于average？ 条件1：7个的average 小于 5个的average 条件2：7个的median 小于 5个的 median

DS：一个三位数xyz是9的倍数，问x+y+z=9？ 条件1：x+y+z<15 条件2：x+y+z>8

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这种ds题目里面有比例关系的我特别弱，老师能帮我梳理一下这种题拿到药怎么入手吗

老师这个题目帮我讲解一下，机经答案我看了还是不明白。

这个题目机经写的特别复杂，老师能帮我讲一下吗

老师，能帮我梳理一下这个题目吗

题目：of the 200 students at college T majoring in one or more of the sciences, 130 are majoring in chemistry and 150 majoring in biology. If at least 30 of the students are not majoring in either chemistry or biology, then the number students majoring in both biology and chemistry could be any number from a) 20 to 50 b) 40 to 70 c) 50 to 130 d) 110 to 130 e) 110 to 150 问题：这道题能理解到是用集合的知识点，但是无论怎么做都无法突破，得到最后结果。还请老师讲解。谢谢