Help! How to produce abstract thought?

Sorry this is going to be somewhat long. I am trying to get into dental school! I am doing an extra year of study to help me prepare for the competitive year ahead, next year. I did not study chemistry in high school. I am getting tutoring and attending all classes with questions in hand. I can scrape by in exams, retaining the information is not a problem. My problem is all year they teach us one way on how to solve a problem. Then they ask us the same problem but give us different bits of information,during an exam, than they’ve given us during the year to solve it. I can understand what they’re asking of me but I just can’t see it when answering a question, needs a different method from previously learnt. How to overcome this?! With physics and biology it’s almost a step by step method that never changes. I just cannot for the life of me see how to do a different way. Feels like some big trick that everyone gets but me! If you have any tips that would be greatly appreciated. Thank you!