When Stephanie was 13 years old she had 137 baseball cards. Each year for her birthday she got 25 more. Stephanie is now 28 years old. Assuming Stephanie has not lost or destroyed any cards, how many baseball cards does she have now?

512 baseball cards

Step-by-step explanation:

At 13, Stephanie had 137 baseball cards.

There are 28-13 = 15 years between 13 and 28

For those 15 years, she got 25 cards a year.

15 * 25 = 375

In those 15 years, she got 375 cards.

She started with 137, and she gained 375.

137+375 = 512

She now has 512 cards.