#feedback This lesson was super clear and well-explained. Thanks, JY!

I have no idea if this'll help anyone, but one thing I found helpful — particularly for the first three invalid formal arguments — is to find the contrapositive and remind myself that contrapositives are logically valid. Maybe it's because I've been so steeped in Lawgic, but I'm constantly finding myself trying to find contrapositives, so much so that it's almost automatic. But, seeing a contrapositive next to the original form of an argument, and then contrasting that with the invalid formal argument listed above, really helped crystalize why the invalid arguments are, in fact, invalid.

#feedback

The first argument in this lesson has a word missing. Instead of reading "...some students in Mrs. Stoops are invited...," it should read, "...some students in Mrs. Stoops' class are invited..."