A box of shortbreads cost $7 while a box of cookies cost $19. Each box contained either 6 shortbreads or 7 cookies. Kimberly bought the same number of shortbreads and cookies. She paid $455 more for the cookies. How many boxes of shortbreads did she buy?
To make the number of shortbreads and cookies that Kimberly bought the same, find the LCM of 6 and 7.

LCM of 6 and 7 = 42

Cost of 1 set of 42 shortbreads
= 7 x 7
= $49

Cost of 1 set of 42 cookies
= 19 x 6
= $114

Amount that Kimberly paid more for 1 set of 42 shortbreads than 1 set of 42 cookies
= 114 - 49
= $65

Number of sets of $65
= 455 ÷ 65
= 7

1 set of $65 → 7 boxes of shortbreads

7 sets of $65 → 7 x 7 = 49 boxes of shortbreads

Number of boxes of shortbreads that Kimberly bought = 49

Answer(s): 49