Student or Learner
What are the difference between those sentence?
1. There can't be many people who haven't had difficulty putting up a tent at some time
2. There isn't many people who haven't had difficulty putting up a tent at some time
First, #1 is grammatical. #2 is not. Isn't is singular. People is plural (for person). The verb and noun should always both be singular or both be plural.
Second, they have different meanings.
- There can't be means it's impossible. There can't be oak trees growing on the moon.
- There isn't and there aren't simply mean it's not true. It might be impossible (There aren't oak trees on the moon) or possible (There isn't a TV in my apartment).
Though it is an assumption about the impossibility here- the person doesn't know it for a fact.