Answer to Question #63074 in Statistics and Probability for Gagarious

Question

A table has drawers. Drawer 1 contains two red and five black biros, draw 2 contains four red and three black biros and drawer 3 contains on red and six black biros. A drawer is chosen at random and a biro is chosen from the drawer. Find the probability that the biro chosen is from drawer 1 if the chosen biro is black