Tierra and joey shared some stamps in the ratio 7: 5. tierra gave joey 12 stamps. if each of them had the same number of stamps in the end how many stamps did tierra have in the beginning?

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.