254)the most difficult question in my test: survery of 800 students to two things’s attitude---- M and R the response can be YES, NO, Not sure the table in the question tells us that: to M: 500 Yes;200 No; 100 not sure to R: 400 Yes;300 No; 100 not sure 200 only reply Yes to M ; ask what is the number of student who do not reply either Yes ? ------------ I get 200 答案: 200 思路: [Tessi] 在 to ”M: 500 Yes “students 中, 有200 only reply Yes to M, 就是说,这200人不reply YES to M, therefore, they are among the students "to R: 300 No; 100 not sure"======> 在 ”to R: ;300 No; 100 not sure“ students 中, 有300+100-200students will not reply to M as YES too. because 在 ”to R: ;300 No; 100 not sure“ 这400 students , don't reply to M as Yes, therefore, the students don't reply YES to either M or R should be 200