You're a little late. But if you want some short, quick rules, then these are a couple that I would take in with me (stored only in my brain, of course):
-- If something is not accelerating or moving at all, then all the forces on it must add up to zero. That could even mean a hanging rope.
-- In a vertical rope, the tension in it is the same everywhere in the rope. The tension is the weight of whatever is hanging from the bottom.
That's really all I'm sure of, based on your hazy, fuzzy description of what you've been doing in class. I don't want to get into things that you might not have learned yet, and confuse you.
You're absolute best bet is to read and re-read the entire chapter one of the book. This is for an absolute best strategy. On the other hand, there are usually key words and terms that are highlighted that most teachers use as a frame for test taking. Studying those highlighted words would be the next best bet. If there are no highlighted words, tough luck. You need to figure out what is important. Which is part of the learning process, and also why I won't directly answer your question. I care more about you learning than you getting a good grade.
The force that acts on hydraulic machine is heavy therefore the content must be something that cannot be compressed by that kind of force, the gas can easily be compressed while a liquid is nearly impossible to.
