can / cant

I can't tell you how much I'm looking forward to the summer.
I can tell that you haven't slept much. 
I can't open this jar of pickles.
I can open this door to let some air in if you want. 
I can swim very well
I can't swim without goggles.
She can speak three languages fluently.

We can't attend the party on Saturday.

We can cook delicious meals together.

He can't believe what he just heard.
Can you believe it?  They promoted me!

Can you help me with my homework?
Can't you see that it is unfair? 

The cat can climb trees effortlessly.

I can't solve this math problem without assistance.

Can we meet at the coffee shop tomorrow?

Unfortunately, I can't make it to the meeting this afternoon