Помогите пожалуйста решить д\з. Ничего не понимаю.

2.
1. couldn't. 
2. could. 
3. couldn't
4. could.
5. couldn't
6. could.
3.
1. Could you play chess when you were ten years old? 
2. Could you ride a bike when you were six years old?
3. Could you send a text message when you were two years old? 
4. Could you swim when you were eight years old? 
5. Could you speak English when you left primary school?