John buys 3 boxes of burritos.  He gives away a 3rd of them to his friend.  Each box has 20 burritos.  He eats 3 burritos per day for 10 days.  How many burritos does he have left?
He gave 3/3=<T>divide(3, 3)=1.0 box away
So he has 3-1=<T>subtract(3, 1)=2 boxes
So he got 2*20=<T>multiply(2, 20)=40 burritos
He ate 3*10=<T>multiply(3, 10)=30 burritos
So he has 40-30=<T>subtract(40, 30)=10 burritos left
