The cost of a shirt decreases by 18%. After the discount, the shirt costs $61.91. How much did the shirt cost before the
discount?

Among the most famous of all meteor showers are the perseids, which occur each year in early august. in some areas the frequency of visible perseids can be as high as 40 per hour. given that such sightings are poisson events, calculate the probability that an observer who has just seen a meteor will have to wait at least five minutes before seeing another.