Ineed with my add and subtraction fraction

The last time i bought this product , it cost $20.00 but it looks like it cost 29. 60 today? what is the increase

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.

Acircle has a circumference of 28.36 units what is the diameter of the circle