John works 12 hours every other day.  He gets a 30% raise from his former $20 an hour job.  How much does he make in a 30 day month?
He works 30/2=<T>divide(30, 2)=15.0 days
So he works 15*12=<T>multiply(15, 12)=180 hours in the month
He got a 20*.3=$<T>multiply(20, 0.3)=6.0 an hour raise
So he gets paid 20+6=$<T>add(20, 6)=26 an hour
That means he makes 26*180=$<T>multiply(26, 180)=4680
