can someone explain why the negation of intersecting sects and proper notation is useful for the lsat?

I dont understand why they breakdown the kumar example with logic diagram with the if when that was previously covered.

#feedback this video needs to have the logic breakdown of only if with the kumar example!

this was truly a mindfuck....

I only somewhat understand it, and figure that kumar must not be a student, he could be a teacher or teacher assistant.

I'm having trouble with the sufficent v necessary identification in the kumar passage

#feedback please edit the video with notation of logic of the specific kumar example.

Sufficiency and Necessity exist only in relation to eachother.

(subset) and (superset)

So annoying, bombed all of them. How crucial is this skill? I'm a native english speaker, and feel like this is just background knowledge, but get stumped when explicity asked what it is specifically related to.... even though I get the gyst of the argument.