can/be able to

She can swim very fast

• She is able to swim very fast.

• It was possible for her to swim very fast.

I can't finish this project on time

• I am unable to finish this project on time

• It is possible for me to finish this project on time

They could solve the problem quickly

• They were able to solve the problem quickly.

• It was impossible for them to solve the problem quickly

He couldn’t lift the heavy box

• He was able to lift the heavy box.

• He was unable to lift the heavy box.

We can complete the task before the deadline

• 1. We are able to complete the task before the deadline.

• We are unable to complete the task before the deadline

1. She couldn’t attend the meeting yesterday.

• 1. She wasn’t able to attend the meeting yesterday.

• It was possible for her to attend the meeting yesterday

1. You can join the conference if you want.

• You were unable to join the conference if you want.

• 1. You are able to join the conference if you want.

He could understand the instructions easily

• He was able to understand the instructions easily

• He was unable to understand the instructions easily.

1. He can't reach the top shelf.

• He is able to reach the top shelf.

• He isn’t able to reach the top shelf.

They can’t find the document

• They are unable to find the document

• They are able to find the document