我有幾條數學問題呀..得5得幫下我...plz..(急)!!

A college dormitory houses 210 students. This Fall, rooms are available for 76 freshmen. On the average,95% of those freshmen who request room applications actually reserve a room.How many room applications should the college send out if it wants to receive 76 reservations? Ans:80


As a fringe benefit for its employees, a company established a vision-care plan. Under this plan, each year the company will pay the first $35 of an employee's vision-care expenses and 80% of all additional vision-care expenses, up to a maximum total benefit payment of $100. For an employee, find the total annual vision-care expenses covered by this program. Ans:116.25


The inventor of a new toy offers the Kiddy Toy Company exclusive rights to manufacture and sell the toy for a lump-sum payment of $25,000.After estimating that future sales possibilities beyond one year are nonexistent, the company management is reviewing an alternative proposal to five a lump-sum payment of $2000 plus a royalty of $0.50 for each unit sold.How many units must be sold the first year to make this alternative as economically attractive to the inventor as the original request?[Hint:Determine when the incomes under both proposals are the same. ] Ans: 4600


A land investment company purchased a parcel of land for $7200. After having sold all but 20 acres at aprofit of $30 per acre over the original cost per acre, the company regained the entire cost of the parcel. How many acres were sold? Ans:60

我計5到佢地ge ans~~ plz...help