请教求助一道OG 数学题

kisscedric

	Favorable	Unfavorable	Not Sure
Candidate M	40	20	40
Candidate N	30	35	35

The table above shows the results of a survey of 100 voters who each responded "Favorable" or "Unfavorable" or "Not Sure" when asked about their impressions of Candidate Mand of Candidate N. What was the number of voters who responded "Favorable" for both candidates?

(1) The number of voters who did not respond "Favorable" for either candidate was 40.

(2) The number of voters who responded "Unfavorable" for both candidates was 10.

OA：A

A选项推出来投票both的 40+30-（100-40）=10人。这没什么问题

我的疑惑：既然是100人投票，且每个人都要对M和N发表意见。那么条件一里面说，没有投出Favorable的人是40人(无论是M还是N）。那么也就是说，Unfavorable        和Not sure对应的四个格子，是这40个人投出来的结果。那怎么投出来的啊？即使这40个人每人对M和N分别发表意见，Unfavorable和Not sure这加起来应该等于80         票啊。【我是纠结于为什么40人投出了 20+40+35+35=130票】这不是矛盾了么.......

求助NN答疑解惑一下。。。。。十分感谢

qx24601

投出favorable的人对另一个候选人也能投别的啊...