Can, could and was/were able to
We use could to talk about an ability somebody had in the past.
We use was/were able to to talk about a specific event in the past.
It was very windy last weekend so I could sail my boat very fast.
Last Saturday evening it was raining so he didn’t go for a walk.
He could sunbathe every weekend last summer because it was very hot.
He was able to ride a bike to work last week because it was sunny.
They couldn’t drive to work today because it was too foggy.
They were able to build lots of snowmen last winter because it snowed a lot.
We can also use managed to in place of was/were able to.
He was able to get a suntan lying in the sun.= He managed to get a suntan lying in the sun.
I was able to have a day off school because the weather was so bad. = I managed to have a day off school because the weather was so bad.