Answer:
By whom was she taught such things?
Step-by-step explanation:
An active voice is when the subject performs the action/ verb whereas a passive voice is where the verb acts upon the subject. And the verbs are changed accordingly.
In the given sentence "Who taught her such things?", the word "who" is the subject which is changed to "by whom". And since the verb "taught" is the second form and third form of the same verb "teach", there will be no change in it.
Therefore, the final sentence in passive voice will be
By whom was she taught such things?