Mary made 20 more coffee muffins than blueberry muffins. After she gave away ²₅ of the coffee muffins and ¹₅ of the blueberry muffins, there were an equal number of coffee muffins and blueberry muffins left. How many coffee muffins did she give away?

	Coffee muffins	Blueberry muffins	Difference
Before	5x4 = 20 u	5x3 = 15 u	5 u
Change	- 2x4 = - 8 u	- 1x3 = - 3 u
After	3x4 = 12 u	4x3 = 12 u

Fraction of coffee muffins left
= 1 - ²₅
= ³₅

Fraction of blueberry muffins left
= 1 - ¹₅
= ⁴₅

The number of coffee muffins and blueberry muffins in the end is the same. Make the numerators the same.  LCM of 4 and 3 is 12.

³₅ of coffee muffins = ⁴₅ of blueberry muffins
¹²₂₀ of coffee muffins = ¹²₁₅ of blueberry muffins

Number of more coffee muffins than blueberry muffins at first
= 20 u - 15 u
= 5 u

5 u = 20

1 u = 20 ÷ 5 = 4

Number of coffee muffins that Mary gave away
= 20 u - 12 u
= 8 u
= 8 x 4
= 32

Answer(s): 32