how do i solve rcs

To be honest there's no magical formula for RC's so only way to improve is to practise it extensively. Do not solve RC's with timer in the beginning. Just read the passage again and again till you understand it entirely. Then go on to answer the questions. Your focus should be to get all the questions right. Once you start getting a accuracy of greater than 85% then move towards speed. Also do read the explanations of the questions you got wrong. This will help yu avoid those mistakes in future.