Abby and Hakeem had the same number of CDs. After Abby gave away 28 CDs and Hakeem sold 17 CDs, the ratio of the number of Abby's CDs to the number of Hakeem's CDs became 2:3. How many CDs did they have altogether in the beginning?

Answer 1

a = h
(a - 28) / (h-17) = 2/3
3 a - 84 = 2 h - 34
so
3 a - 2 h = 50
but we all know a = h so
a = h = 50
so they had 100

Answer 2

they both start with x CDs, and then
(x-28)/(x-17) = 2/3
find x, and then their starting total is 2x