There are 9 students in a class: 5 boys and 4 girls. If the teacher picks a group of 4 at random, what is the probability that everyone in the group is a boy?

Suppose that 3% of all athletes are using the endurance-enhancing hormone epo (you should be able to simply compute the percentage of all athletes that are not using epo). for our purposes, a “positive” test result is one that indicates presence of epo in an athlete’s bloodstream. the probability of a positive result, given the presence of epo is .99. the probability of a negative result, when epo is not present, is .90. what is the probability that a randomly selected athlete tests positive for epo? 0.0297

Can you me find the missing length. i attached an image.

Someone me! if you’re smart you can solve this!