First you will have to calculate how much she spends on the songs per month so you will have to times how many songs she purchases (10) by how much they cost ($0.99) so
10x$0.99=$9.90
then you will need to times the amount she spends per month ($9.90) by how many months (8)
$9.90x8=$79.20
last you will need to add the amount she paid to join ($15.50) and the total amount she payed on songs in 8 months ($79.20)
$15.50+$79.20=$94.70
so the total amount she spent after 8 months is $94.70
