when you summarize the negate/sufficient rule, why do you drop the "take the contrapositive" rule #5? it makes it seem like its not required

Try to take a practice exam section, just thirty five minutes timed to push through and see where you are. If you do well then awesome and if not, hopefully it’ll push you to study just a couple hours each weekend day to raise that score. You’re here so clearly you know you want something different in your life. Easier said than done but change must come from you :)

#help... is it wrong to use the group 3 conditional where it says "unless" to figure this out?