The ratio of Joe's CDs to Peggy's CDs was 5:3. After Joe gave Peggy half of her CDs, Peggy had 18 more CDs than started with. How many CDs did Peggy get from Joe?
Let Joe's CDs =J
Let Peggy's CDs=P
5P+.5J=.5J + 18, solve for J, P
P = 18 CDs that Peggy started with
J = 30 CDs that Joe started with. So Joe gave Peggy:
30/2 = 15 CDs.