The English expression "fair enough" can be used to concede a point in an argument, or acknowledge the other person's position, without expressing complete agreement. To take an example from UrbanDictionary (surprisingly the best example I could fine):
Bro A: Dude, why didn't you take that job? The benefits were killer!
Bro B: Maybe, but it was so far out, I'd have spent more on gas than what they were willing to pay me.
Bro A: Fair enough.
Bro A does not necessarily agree with Bro B's decision, but he acknowledges his position and does not want to try and talk him out of it.
A similar situation is one in which one person is critical of another, but is rebuffed by a counter-criticism:
Bill: You really shouldn't drink so much. It's bad for your liver.
Jill: Don't you smoke a pack of cigarettes every day?
Bill: Fair enough.
In this case, Bill is acknowledging he's not in a position to be criticizing Jill's behavior.
In Chinese, what might be used to express the same idea as "fair enough" does in these conversations. I doubt it has to do with 公平
.
Edit:
Another similar English expression is "You have a point", which expresses "You have a good argument, even though I might not agree with your conclusions".