A hard mathematics problem, a mathematics problem with is a hard nut to crack
- bài thi sinh vật khó nuốt lắm: The biology paperis very hard to do, the biology paper is stinker
- khó nuốt: Hard to eatCơm khô khó nuốtDry rice is hard to eat.(thông tục) Hard to dọBài thi sinh vật khó nuốt lắmThe biology paperis very hard to do; the biology paper is stinkerBài toán khó nuốtA hard mathem
- tàu bốn ống khói: four funnel liners
