Maggie

Ok...I am not quite sure where I'm going with this...Could you be more specific?

If I is false then the second premise (F ∨ G) → (I ∧ J) must be false because I and J both have to be true for (F ∨ G) to be true?

Ok...so I need to assume and get a contradiction?

Ohh...if ¬K is false that means I ↔ ¬K is false because I if only if ¬K.

¬K is false...?

We know that K and ¬K is a contradiction?

I'm sorry, the program is called Fitch. And my problem is I do not know how to start a proof...I don't know what subproof does. If I was asked to write the proof out on a piece of paper I would have no idea how. Using the program helps to check my steps as you can see above. However I just don't understand the proof process. And yes, I don't see how to work from K to H...

When it comes to formal proofs I have no idea how to even start it. When do I use a subproof and how to use it? Can someone please explain to me when to use a subproof and how to start a formal proof? Please and thank you. This is what I have so far...and I have no idea what to do next...