Joff must kill B OR R : And if he doesn't kill R, he must kill B. (B or R = If NOT B, then R.)

#feedback maybe there could be examples for each of these types one more time. Just to help reinforce the ideas.

For questions like 7.1 and so on, are we still supposed to do a contrapositive? Why weren't these included in the example? Is that only done for necessary?