Question

Les encanta esquiar en invierno.

Answer 1

I spot only two errors here.
There is a grammatical error in the first sentence - it should say en el invierno (just like the other two sentences), rather than just en invierno. 

The third sentence doesn't have a subject; are you supposed to add one? Following the pattern of the other two sentences, you could say:

Les gusta patinar sobre hielo en el invierno.

The verbs (esquiar, nadar, patinar) are all in infinitive form, which is correct in this context. When you are speaking of things you like to do, you say "I like to swim". Spanish is the same: Me gusta nadar. (Both use the infinitive.)

I hope this helps; good luck.