-(으)ㄹ게요 and -(으)ㄹ 거예요 both mean "I will", but -(으)ㄹ게요 is only for a promise or decision made in response to the listener. Use -(으)ㄹ 거예요 for reported plans, other people's plans, and questions.
Learners can form -(으)ㄹ게요 correctly (spelled 게, not 께) and choose between it and -(으)ㄹ 거예요.
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