James pays $1000 for advertising.  It brought 100 customers to his site and 80% of those bought something at the store that cost $25.  How much profit does he gain from the ad?
100*.8=<T>multiply(100, 0.8)=80.0 customers bought something
That means they were worth 80*25=$<T>multiply(80, 25)=2000
So he gained 2000-1000=$<T>subtract(2000, 1000)=1000 from the ad
