I have to translate this single phrase using pronouns: "What do you (sg.) think about him?"
My answer:
Quid tu de eo cogitas?
My answer:
Quid tu de eo cogitas?
cogitare de to think about someoneDoesn't cogitare aliquid mean "to thing about something"? I think it's safer to express the idea of opinion using censes or arbitraris.