Carter is going away to college and is giving his collection of 531 baseball cards to his cousins. I

Carter is going away to college and is giving his collection of 531 baseball cards to his cousins. If he gives 227 cards to Lewis, 186 cards to Benny, and 18 cards to Seven, how many cards are left over?

When Carter gives away cards, he subtracts from his collection. So we have:
531 - 227 - 186 - 18 = 100 cards leftover