Simon had some blueberry cookies and strawberry cookies. ⁵₆ of the number of blueberry cookies was equal to ¹₃ of the number of strawberry cookies. After Simon made -12 more blueberry cookies, the number of blueberry cookies was ¹₅ of the number of strawberry cookies. How many cookies did he have altogether in the end?
Make the numerators the same. LCM of 5 and 1 is 5.

56 of blueberry cookies = 1x53x5 of strawberry cookies

⁵₆ of blueberry cookies = ⁵₁₅ of strawberry cookies

	Blueberry cookies	Strawberry cookies	Total
Before	6 u	15 u
Change	+ -12
After	1x3 = 3 u	5x3 = 15 u	18 u

The number of strawberry cookies remains unchanged.  Make the number of strawberry cookies the same.  LCM of 5 and 15 is 15.

Number of more blueberry cookies made
= 3 u - 6 u
= -3 u

-3 u = -12

1 u = -12 ÷ -3 = 4

Number of cookies that Simon had in the end
= 3 u + 15 u
= 18 u
= 18 x 4
= 72

Answer(s): 72