How to correctly apply "in which", "of which", "at which", "to which", etc? [closed]

The trick to knowing how to use; of which, at which, in which, to which, from which is to analyse the prepositional phrases, phrasal verbs, verbs and prepositions:

1. He /spoke of/ war and peace and many other topics that day.
   The topic /of which he spoke/ was complex.
   The verb here that means to speak about a topic is /to speak/ of a topic/: to mention

2. The party /at which/ he spoke/ was noisy.
   Phrase: A party is held /at a place/. It is implied.
3. The situation /in which/ we found ourselves was dire.
   Phrase: /to find oneself /in a situation.
4. The bonds /from which/ we broke free were tight.
   phrase: to /break free/ from bonds.
5. The town /to which/we were driving was 50 ks away.
   phrase: to /drive/ to a place.

Summary (and not a complete answer but a general one): The preposition depends on the verb that takes a preposition, a phrasal verb that includes a preposition, or it depends on the prepositional phrase used. Also, there are many other prepositions that can be paired with which: under, during, about, over, etc.

Probably easiest to explain through examples. Each phrase simply means "the thing that we've already mentioned", e.g.

• The box in which the books are kept

• The town of which we were speaking

• The time at which we will arrive

• The destination to which we were heading

I'm sure there's a grammatically-correct term, but they're really just the correct forms of "the box the books are kept in"/"the town we were speaking of", i.e. removing the trailing preposition.