Please help quickly thanks :)

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.

What is always true when two whole numbers are subtracted?

Find the distance between c and d on the number line c=3 and d=11