John buys 20 hours of music a month.  The average length of a song is 3 minutes.  He buys each song for $.50.  How much does he pay for music a year?
He buys 20*60=<T>multiply(20, 60)=1200 minutes of music a month
So that is 1200/3=<T>divide(1200, 3)=400.0 songs
That means he pays 400*.5=$<T>multiply(400, 0.5)=200.0 a month
So it comes out to 200*12=$<T>multiply(200, 12)=2400 a year
