It is estimated that 20 patrons will attend an event for every $100 spent in advertising. if tickets cost $40, how much can a promoter expect to increase sales if he spends $10,000 in advertising?

20 patrons for every $100.

So when you have $10,000 that will be 2,000 people.

The tickets cost $40 for 2,000 people, the total is $80,000.

The promoter spent $100 advertising, so he gets 800 times more in increase.