What is the average of -18.75 and 200.25?

Need this asap if anyone can i would be very grateful. if you could show workings that would really

Oscar and julie ashton are celebrating their 15th anniversary by having a reception hall. they have budgeted $4,500 for their reception. if the reception hall charges a $90 cleanup fee plus & 36 per person, find the greatest number of people that they may invite and still stay within their budget.

Write the rational number in lowest terms 99/-15