왜 (으)니까
When someone asks me a question using 왜 like this "왜 못 가요?" Can I answers using (으)니까 like "바쁘니까 못 가요"?

Question

왜 > (으)니까
When someone asks me a question using 왜 like this "왜 못 가요?" Can I answers using (으)니까 like "바쁘니까 못 가요"?

Answer

Correct! You can also answer like -서 못 가요 For example. 바빠서 못 가요.

I would say that the way that I just told you is more common.