In a box there are 6 red, 8 green, and 10 white balls. if three balls are selected simultaneously and at random and the color is noted find the probability that all are green given that all are the same color?

The distribution of the amount of money spent by students for textbooks in a semester is approximately normal in shape with a mean of $235 and a standard deviation of $20. according to the standard deviation rule, how much did almost all (99.7%) of the students spend on textbooks in a semester?