after i ask : wat is Z~N(xx,xx)

Today i asked lecture about the statistic quiz.

wat is Z~N(xx,xx)

Then guess wat. All the students after tat said :" ya, wat is tat. i nvr see b4."

my lec said : " i got teach u all b4 mah, not yr class meh ?"

everyone said : " no , u nvr teach us."

ALL RITE , WHAT SHOULD I DO ? IT IS SO UNFAIR. I'M FRANKING ANGRY AND SAD.