I need help to understand when to switch & negate a valid conclusions on contrapositives. The videos from Invalid Argument Forms are confusing and are just not clicking. When I think I know how to "draw valid conclusions w/ transitions AND w/ intersection statements" I suddenly don't and don't know what I'm doing wrong. Can anyone suggest the videos or any other methods to review to understand the material?

Ever since we got to this section, I've been confused.