Math Word Problems....I hate them!!?

In order to raise money for renovations, the directors of an old age home decided to put on a play for three consecutive nights. The directors plan to charge $3.50 admission per person. They hope to raise $1750 from the event. Seventy people bought tickets the first night and 210 people bought tickets the second night. How many people must buy tickets on the last night so that the directors may reach their goal?