Let us assume the number of CDs your friend has = n
Then
Number of CDs that you have = n + 11
It is already given that the number of CDs you have = 30
Then
n + 11 = 30
n = 30 - 11
= 19
From the above deduction, it can be easily concluded that the correct option among all the options that are given in the question is the fourth option or option "D". I hope that the answer has actually come to your desired help.