Jasmine sold half of her Barbie doll Collection and then bought 9 dolls. She now has 13 dolls.
Barbie dolls did she begin with?
How many

8 dolls.

Explanation: 13 - 9 = 4, 4 x 2 = 8.

Work the equation backwards... she has bought 9 extra dolls to add on the the half of her original amount. Without the extra 9 dolls (13 - 9), Jasmine has half of her original amount left (4) and so to find the original amount of dolls, think that if 4 is half the amount, what is 4 half of? 4 is half of 8 and so 8 is the original amounting dolls she had.