"This is correct."
Benar has a stronger meaning than betul. It can contain some sense of "moral". For example, "You did the right thing", "God shows the right path", "You made the right choice", in these contexts, it would be more correct to say benar. Meanwhile in "Your answer is correct", "It's true", "That's right", it is okay to say betul, or benar too. It's like, in sentences where you can use betul, benar can also be used. But in sentences where we're supposed to use benar, it doesn't mean you can use betul. "Benar" covers both meaning of benar and betul, but "betul" is not strong enough to cover the meaning of "benar".