Welcome to the most standard "trick" students use to get answers out of professors/TAs :).
My answer is as a professor, but I think the basic principle works for TAs as well. What I usually do is turn the question back to them. Something like:
S: Is this answer correct ?
Me: Well, what do you think ?
now things can go in different ways:
case 1: S says "well I'm not sure". In which case you can say, "well how might you go about verifying that your answer is correct" ? this might then lead to a discussion of how to check answers without you having to commit to commenting on their particular answer.
case 2: S says "Well I think it's correct". Then you can say "Ok then :). I understand that you think it's correct" and leave it at that.
They might persist and say "can you tell me if you think it's correct". At which point you can say "No, but how would you go about checking its correctness" taking you back to case 1 and the "methodology" of checking.
The underlying pedagogical point is this: you don't want students checking answer correctness with you ahead of time because
a) learning to check your own answers is an important part of learning. It allows you to diagnose problems and identify the correct path to an answer.
b) it's unfair to those who don't ask, and it's a waste of your time
c) using this socratic approach allows you to assess how they are approaching the problem, and allows you to guide them in their approach, rather than spoonfeeding a prescribed answer. Everyone approaches problems differently.
p.s Students often also ask for hints. The material I teach is usually mathematical, so they're asking for hints for a proof. There you have some more leeway, but the trick is to draw them out into explaining their thought process, and then trying to gently nudge them without revealing the answer. It takes some practice and a lot of Socratic dialogue.