Go to your instructor very calmly and simply ask him "can you go over this problem with me slowly?". Most instructors/teachers, no matter how arrogant, have not turned me down. While he or she is going over the problem, continuously ask the question "why?". It might sound like a stupid question but it makes the teacher (or whoever for that matter) explain it more. Along with asking for help, I find that reading background information in science helps me. It will give you more understanding on why the equation is set up that way and what the teacher is thinking. If nothing else, do not attempt to figure it out when stressed out to your limit or are miraculously awake at three in the morning. You wont pick up any new information and your just going to say screw it and chuck your book out your window. Been there, done that, never again. Take a breather and try it later. Hope this helps.