Ashley was going to sell all of her stamp collection to buy a video game. after selling half of them she changed her mind. she then bought nine more. how many did she start with if she now has 39?

Well in this problem we just have to work backwards doing everything opposite of what she did in order to get the final answer.
so she has 39 stamps at this moment. and since she bought nine more stamps lets subtract that value to see what she had before that.
 1.) 39 - 9 = 30
now she has 30. but she said that before step one she sold half of them to buy that video game. so she divided her starting number by two. so again we are going to work backwards by multiplying the number by 2:)
2.) 30 x 2 = 60!!
3.) So she started out with 60 stamps 
answer is 60:)
hope i helped