Hey there!
Let's say that Julia has 50 CDs. We would plug this into c in the expression we've been given to find the number of CDs that Ahmed has.
c = 50
1/2c + 5
1/2(50) + 5
25 + 5
30
So, if Julia has 50 CDs, Ahmed has 30. We used the expression to figure that out and, therefore, that's why it was created.
Your answer will be the number of CDs that Ahmed has.
Hope this helped you out! :-)