The answer and equation is 17 - 19 = -2
subtract the fee from the total to get the amount actually spent on songs
23.80-7 = 16.80
divide that amount by price per song to get number of songs downloaded
16.80 /0.20 = 84 songs
1/3(9x) =3x
1/3(18) =6
3x+6-5
Then you do
-(x)=-x
-(3)=-3
5x-x-3 = 4x-3
4x-3=3x+6-5
4x-3=3x+1
x=4