1. The problem statement, all variables and given/known data A class is given a list of 20 study problems from which 10 will be on an upcoming exam. If a student knows how to solve 15 of the problems, find the probability that the student will be able to answer (a) all 10 of the questions on the exam. (b) exactly 8 questions on the exam, and (c) at least 9 questions on the exam. 2. Relevant equations 3. The attempt at a solution Well for a I found 20C10 which is the total possible combinations of questions that could be on the test then I found 20C15 which is the total number of combinations of the problems the student solved. Would you divide 20C15 by 20C10? I'm not sure how to solve this problem.