In the game, each student has his or her own card. The "I have" number is going to be an answer to a question someone asks. The "who has" question is the question that a student gets to ask once an answer has been given.
In the card above, the student would answer if they heard the question, "Who has 24-10?" The student would then say, "I have 14. Who has 54 + 10?" and wait for a student to say, "I have 64."
Sometimes we time students, sometimes we do it just for fun. Our favorite set of cards are the plus or minus 10 cards. Each card in that deck requires a student to add or subtract 10 from any number 1-99 like the sample above.