P: not C → not XP: ? C: X → not D

michaelpeoples93 January 16, 2020

Hw to solve for D > Not C

I did the contrapositives of the premise and the conclusion and was stuck between answer choices a/b/c. What's the best way to solve at that point?

Replies

Create a free account to read and take part in forum discussions.

Already have an account? log in

Ravi January 17, 2020

Hi Michael, the best way to solve this question is to make sure your anticipation is rock-solid before going into the answer choices.

We have

P: not C - >not X
P:
C: X - >not D

Not D is appearing in the conclusion for the first time, so we know that the missing premise will have it.

Let's do the contrapositive of the first statement to get X on the sufficient side of the chain

P: X - >C
P:
C: X - >not D

How could we get to not D? If we added C - >not D, we could validly conclude X - >not D

P: X - >C
P: C - >not D

X - >C - >not D

C: X - >not D

Now we just have to look for the answer choice that matches our anticipation, which is C - >not D, and that will be the correct answer.

Does this make sense? Let us know if you have any other questions!

michaelpeoples93 January 21, 2020

Makes a lot of sense. Thank you!

Mikebuck89 June 5, 2020

Currently this is saying I'm incorrect and it's stating that D--> Not C is the correct choice … Bug ?