P: not A → not BP: B–most–XC: ?

dnturner September 1, 2017

Rule #2?

Given Rule #2 with quantifiers, why are we able to make a valid deduction if the two lines don't have the sufficient condition in common?

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Mehran September 3, 2017

Hi @dnturner, thanks for your post.

Consider each given premise, and its contrapositive (if applicable).

P2: not A ==> not B

CP: B ==> A

P2: B-most-X

OR: X-some-B (remember: no contrapositive here, and "most" reverses as "some")

C: ?

You can combine the statements as follows:

X-some-B==>A

Thus, X-some-A

This is answer choice (C).

Hope this helps! Please let us know if you have any additional questions.