Use able to / unable to

1. I can play. (Use able to) 

Ans. I am able to play.  

2. I could play (Use able to) 

Ans. I was able to play.  

3. He could tell me. (Use able to) 

Ans. He was able to tell me.  

4. They could tell me. (Use able to) 

Ans. They were able to tell me.  

5. She can work. (Use able to) 

Ans. She is able to work.  

6. I can write a letter. (Use able to) 

Ans. I am able to write a letter.  

7. She could eat a mango. (Use able to) 

Ans. She was able to eat a mango.  

8. She could not eat sandwich. (Use unable to) 

Ans. She was unable to eat sandwich.  

9. I cannot dance. (Use unable to) 

Ans. I am unable to dance.  

10. I cannot write an essay. (Use unable to) 

Ans. I am unable to write an essay.