Step-by-step explanation
Step 1
Let
C represents the total cost
S represents the number of songs
one -time registration fee means you dont have to pay this anymore, no matter how many songs you buy
charges for one song=0.49
charges for S songs=0.49*S
then
total cost= one-time registration fee plus 0.49 dollars per song
replacing
I hope this helps you.
Step 2
the total cost for 15 songs
c(15), you have to replace 15 in the place of S
So, the cost of the 15 songs is $21.3