Can you give me some step-by-step instructions for this math problem: Janessa has a plan to give her brother Dexter his first collection of baseball cards. She currently has 4 cards in addition to the 13 that her father gave her.  She ordered a collection of 36 cards from eBay. After inspecting the cards she found 4 cards are in bad shape and decides to throw them away. Janessa ended up giving Dexter 29 cards. How many cards did Janessa keep for herself?