Word/Expression: a piece of cake
Quick translation: Very easy; no problem
A: How was the examination?
B: It was a piece of cake.
A: 시험 어땠어?
B: 정말 쉬웠어.(누워서 떡먹기) <- 잘못 먹다가 목 막혀 죽을 수 있습니다.^^;
Possible interpretation: Literally, eating a piece of cake is easy because it is delicious.