So here is how you find the answer of the given problem above. Given that y = number of CD that Michael has and x is John's. So x = 15 + y The total of their CDs is 55. 55 = 15 + y 55 - 15 = y So y = 30 x = 15 + 30 x = 45 Therefore, John's number of music CDs is 45 and Michael has 30. Hope this answer helps. Thanks for posting your question.