Answer: Probability that an athlete uses steroids given that he tests positive is 91.6%.
Step-by-step explanation:
Let A be the event that athletes test positive for steroids .
Let B be the event that he actually use steroids.
Since we have given that
Probability that athletes test positive for steroids = P(A) = 12%
Probability that athletes test positive for steroids and actually use steroids = P(A∩B) = 11%
So, we need to find the probability that an athletes use steroids given that he tests positive.
For this we will use "Conditional probability":

Hence, Probability that an athlete uses steroids given that he tests positive is 91.6%.