Broadly speaking, a prepositional phrase might modify almost any element of the sentence in which they are found - though in a complex sentence they are more likely to modify the clause in which they are situated or, when the prepositional phrase is a clause in itself, the clause to which it is most closely attached.
Working out what the prepositional phrase modifies is a matter of looking at meaning. You usually expect it to modify something that is close to it in the sentence, but that's only an indication, a potential tie-breaker.
In the first example, in class is clearly acting as an adverbial. It could attach, grammatically, to any verb in the sentence. It could be delivered, are, or see. Now, are is not something likely to take a location as an adverb, it's not clear what it would mean at all. So did he deliver it in class, or is the likelihood comment about what they would see in class? Either would make sense, but the adverbial is closer to see - and it makes more sense, because class is a closely regimented environment so it is readily expected that there are things that are unlikely to happen in class.
In the second example, it is hard to know without more context - I would guess it would be in explanatory sentences subsequent to this sentence - whether is prepositional phrase is distributed over the and or not. It would, as you have clearly realised, be very unlikely to be intended to attach only to perceived personal importance, because the writer would have put it before the and in that case. As it is, it could attach to either. Of course, there's also another way of parsing it that removes that ambiguity - but there's no obvious reason to conclude that this parse is correct:
Involvement is the level of (perceived personal importance and interest) evoked by a stimulus within a specific situation.
In that case, within a specific situation could attach to stimulus or to perceived personal importance and interest, or to evoked, though the effective meaning of any of those would be similar. That is how I would tend to read the sentence.
For your third example, you have missed a way of parsing it. We have, in that sentence (actually, it's not a sentence, but we'll ignore that for now), three nouns or noun phrases before the prepositional phrase. It could be Prior Net Income, Zero Earnings Benchmark, or effect. Fortunately, "the effect of X on Y" is a common, standard phrase, so we don't even need to think about it, it's just:
The (effect) of (Prior Net Income and Zero Earnings Benchmark) on (cost asymmetry).
So, general rules are hard to state, but these are some tips:
- Look out for standard or set phrases. When a place in such a phrase is taken up by a phrase rather than a word, they can be harder to spot, but you will get the hang of it with practice.
- Look at the possible different meanings, and see what makes sense. Not all prepositional phrases can meaningfully be applied to a given other word or phrase. Remember to use wider context and subject knowledge to help evaluate this.
- When in doubt, think about what is closest to the prepositional phrase - but don't use that as a guide before looking at other factors.