Well, I tackle these sort of problems by writing the truth table (TT) for what needs to be achieved, then look at the TTs for the gates etc that are available and deduce how to make those 'fit' into the main TT - in my head, it sorta works like a crossword puzzle.
Another way to tackle the problem is to write the logic equation(s) for what needs to be achieved and see if the 'structure' of the equations relates back to the gates available for use, thus enabling One to construct what is required - personally, I never could do it well this way, it's too much like Math, which I'm hopeless at.
Does the way that the questions are being asked cause you confusion?
Always keep it in mind that ANY logic problem is only built up from basic building blocks - just like bricks in a house - put them together the right way and you can make anything!
"Give me a few bucket-loads of NAND gates and I could build a you a PC" - that's what I've frequently said to others and, whilst it might sound a little trite, it's basically true. The trick is not to get overwhelmed with the complexity of the problem, always tackle it one bit at a time.
(or one Byte at a time, or one Nibble at a time
<snigger>, sorry couldn't resist that!
)
Hope this rant helps you, let us know how you go.
CJ