Question

half of your baseball card collection got wet and was ruined. You bought 19 cards to replace some that were lost. how many did you begin with if you now have 39

Answer 1

You started with 40 baseball cards.

To find the answer to this problem, you need to work backward. 39(your current amount) - 19(the amount you added) = 20. And if 20 is only half of what you started with, you'd need to multiply 20 by 2, which is 40. So you started with 40.