Benny bought 4 new baseball cards to add to his collection. The next day his dog ate half his collection. There are now only 41 cards left. How many didhe start with?

You work backwards so if half is 41, he had double that before the dog ate half the collection. So he had 82 card after adding 4 new cards so you subtract 4 and your answer is 78 cards.

41 x 2 = 82

82 - 4 = 72