For this case we have the following equation:
 
 Where,
 x: number of people.
 y: the amount of money, in dollars.
 The intersection with the y axis occurs when x = 0.
 We have then: 

 That is, if no one attends, the amount of money is $ 1250. 
Answer:
 If no one came to the dinner, the charity would still raise about $ 1250.