"you 'took' my class" is marked as wrong. Why?
"You took my class" would be "Usted tomó mi clase". Or "Tú tomaste mi clase".
Could this sentence be a command? If so, shouldn't an implied "you" be accepted? In other words why wouldn't "Take my class" be accepted?
Could it be 'attend my class'?
So why isn't it Usted tomas mi clase?
tu tomas = 2nd person informal / Usted toma = 2nd person formal (which uses the 3rd person singular endings)
This is not something a native English speaker would say.
I would say "You attend my class"