I am too weak to read rc and understand it.how can I nail this prosblem

Make sure you read Two newspaper daiky in an hour and watch atleast 1news channel related to financial news everyday. With this you're gaining expertise and command over soft skills and good understanding of all articles with different views. Make sure you solve atleast 10 RC everyday and rectify your mistakes regularly such yhat they are not repeat again and again. With patience and persistent efforts, you will master this section very soon. All the Best for your exams and preparations. Hope it helps.

Read! Read! Read! To ace the RC section of CAT, you need to spend an hour on an average everyday reading. Good comprehension comes from reading with a relaxed mind, one that is receptive to new ideas. It comes from engaging with the author: understanding not just what he says, but why he says it and how he feels about it. Take your time to read the passage, say 8-10 minutes. This will be time well spent if you involve yourself while reading.
Good comprehension comes from the ability to make connections with what you already know. So, read a wide range of subjects - politics, science, economics, philosophy, culture - so that you get comfortable with these topics and don't balk when you see a passage that relates to a topic you don't know much about.  To start with you can read books by these authors: Sidney Sheldon, Jeffrey Archer, John Grisham, Agatha Christie, Mario Puzo, Salman Rushdie, Aravind Adiga and many others. You can also start with newspapers including TOI, ET, Indian Express, The Hindu, HT etc.