Tom broke his leg and needed to go to the doctor.  The visit cost $300 and the cast cost $200.  If insurance covered 60% how much was Tom's out-of-pocket cost?
The cost was 300+200=$<T>add(300, 200)=500
So insurance paid for 500*.6=$<T>multiply(500, 0.6)=300.0
That means he had to pay 500-300=$<T>subtract(500, 300)=200 out of pocket
