When you see the answers to an exam it always looks easy, but that is why you really have to try and think things through before being told. It is the thinking that matters!
More generally, don't see this forum as a place just to get answers, but more to discuss what you think and to question the 'why' of certain things. You will find very experienced folk on here still asking for advice on unusual problems or systems, not always because they don't know but sometimes to walk round the arguments to decide what is the best solution for a given situation.