Cách sử dụng
The expression "a hard/tough nut" is used to describe someone or something that is difficult to deal with or understand. For example, if someone is very stubborn or resistant to change, you could say that they are a hard nut to crack. It can also be used to describe a challenging task or problem that is difficult to solve. In general, "a hard/tough nut" refers to something that is not easily solved or dealt with.