数学题 请把计算过程写出来啊,谢谢~~~~

Question 2
Harrison Water Sports has three retail outlets:Seattle,Portland,and Phoenix.The Seattle store does 50 percent of the total sales in a year,while the Portland store does 35 percent of the total sales.Further analysis indicates that of the sales in Seattle.20 percent are in boat accessories.The percentage of boat accessories at the Portland store is 30 and the percentage is 25 at the Phoenix store.
Please calculate the probability that a sale by Harrison Water Sports is for a boat accessory.(EXPRESS IN % TERMS)
P=20%*50%+30%*35%+25%*（1-50%-35%）=24.25%
Question 3
A merchant paid $300 for a shipment of x identical calculators.The merchant used 2 of the calculators as demonstrators and sold each of the others for $5 more the average (arithmetic mean) cost of the x calculators.
If the total revenue from the sale of the calculators was $120 more than the cost of the shipment,how many calculators were in the shipment?
因为每台收入5元,即卖出的台数N=120/5=24
另有2台是展示机,即购入数量为24+2=26台.