В чем разница между The learnable subjects и The subjects which can be learnt ?Пожалуйста, приведите примеры.

there is a small but important difference.

example:
"Let's talk about maths, physics, Chinese and Spanish. The learnable subjects are taught"

Here, "the learnable subjects" means all subjects that can be learned from the list of maths, physics, Chinese and Spanish. So this could for example only be maths, physics and Spanish, since Chinese is pretty hard to learn.

"Let's talk about maths, physics, Chinese and Spanish. The subjects which can be learned are taught"

In this sentence, you're first saying that maths, physics, Chinese and Spanish can all be learned, then you're saying they can be taught. So here Chinese is not excluded.