We recommend that you do not use these exams to prepare for your own exam. Instead, use them to evaluate your preparation. That is, you should first study as you ordinarily would, without looking at the exams. Then, take an exam: actually write out all the answers. Finally, grade yourself by use of the solutions key. If you did not get all the answers right, then you didn't understand the material, and should study more. It's important to learn the concept behind a wrong answer, but — equally importantly — to think about what other concepts you might also have overlooked and adjust your studying style.
An all-too-common alternative approach is to skim over the exam solutions, and tell yourself that yes, you could have answered that question (without actually trying to answer it). This approach is much less successful, and we do not recommend it.