In a pet shop that only sells dogs and cats, there are x number of animals. Given that there are 10 cats and the probability of choosing a dog at random is P(dog)=7/12. How many dogs are there? Give correct answer and show working out please.

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