I'm sorry, but I can't/won't be able to come to your party next week.
I'm sorry, but I won't be able to come to your party next week.
She ... write a dictation well yesterday and got a bad mark.
She couldn't write a dictation well yesterday and got a bad mark.
I ... finish my work today. I am tired.
I can't finish my work today. I am tired.
The chief can/will be able to see you on Tuesday.
The chief will be able to see you on Tuesday.
I think I can/will be able to speak English quite well in a few month.
I think I will be able to speak English quite well in a few month.
We could/were able to stay with Bob in London last June.
We were able to stay with Bob in London last June.
After a few month on the course she could/was able speak French well.
After a few month on the course she could speak French well.
I ... to help you with English tonight.
I will be able to help you with English tonight.
If you have spare time we ... go on an excursion.
If you have spare time we will be able to go on an excursion.
Не ... explain us anything.
Не can explain us anything.
She could/was able understand everything.
She could understand everything.
She ... dance quite nicely when she was a girl.
She could dance quite nicely when she was a girl.
We ... take the books from the library because it was closed.
We were not able to take the books from the library because it was closed.
I ... see you when you return.
I can see you when you return.
I ... get tickets yesterday.
I could get tickets yesterday.