what's the difference between 못해 & 할 수 없어?
감사합니다~ (\(^-^ )/)

Question

Answer

I think its the same since 못 and 수 없어 both mean " i can't"
  Ex:
한국어를 할수없어요
한국어를 못해요
  but:
when you add 잘 to 못 and to 수 없어요 like 한국어를 잘못해요 it means that you are not good in korean not that you can't speak it at all.
  ^^

Answer

못해 is a short and easy way of saying 할 수 없어.

Answer

못 해요 means "I can't do"I can't do so, it's against my nature 
You can say 안 돼 (i think u should know this too)to mean "It doesn't work" when컴퓨터가 안 돼. The computer doesn't work. (I can't-ㄹ 수 없습니다 is like "There's no way you(or we)"capacity, way, method, ability". It's formal. 
잘 수 없습니다. I can't sleep
.고칠 수 없습니다. I can't fix it.

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