a tough nut to crack in a sentence

Examples

1. Syria is a tough nut to crack and Egypt is definitely interested to help,
2. But Kalicharan is a tough nut to crack.
3. But Vikrman is a tough nut to crack.
4. Vermund said, " It's a tough nut to crack ."
5. Going into the campaign, club officials knew they had a tough nut to crack.
6. It's a tough nut to crack in terms of how to break in.
7. Tikrit was a tough nut to crack.
8. This is a tough nut to crack.
9. Wolvesey was a tough nut to crack.
10. Offaly played almost to exhibition standard at times, although Clare proved a tough nut to crack.