Must is a hard nut to crack, but it has a sweet kernel.

Must is a hard nut to crack, but it has a sweet kernel.

You must crack the nuts before you can eat the kernel.

China is going to be an extremely tough nut to crack.

Economy is half the battle of life. It is not so hard to earn money as to spend it well.

It really is a case of taking a sledge hammer to crack a nut.