Can someone answer. there is one problem. there's a picture. you!

The combination formula nCr=n!(n−r)!(r!)

n is the number of elements (total). 

r is the number of elements picked from the set.

In this case, n = 15 and r = 4

15!(11!)(4!)

=1365

So, there are 1365 ways of listening to the CD's.

Hope I helped!

y=3n + 1

step-by-step explanation:

this is wrong because it says the second number is one less and i added one instead

ok then what happened.