Final answer:
After setting up an equation with the information given, we find that Carlos gave away 10 cards so they both would have the same number of cards left.
Step-by-step explanation:
Carlos started with 30 baseball cards and gave away x cards, while Miguel started with 40 baseball cards and gave away 2x cards. To find out how many cards Carlos gave away, we need to set up an equation based on the information that they had the same number of cards left after giving some away.
Carlos's remaining cards: 30 - x
Miguel's remaining cards: 40 - 2x
Now, we set these equal to each other to solve for x:
30 - x = 40 - 2x
x = 40 - 30
x = 10
Carlos gave away 10 cards.