Найдите вероятность того, что выпал ровно один орёл, если известно, что в трех раза выпал орёл.

This question is contradictory. If it is known that in three tosses an odd number of heads appeared, and we want the probability of exactly one head, this is impossible. If the question meant 'at least one head', then the probability is 7/8. If it meant 'exactly one head', and the condition is 'at least one head', then the probability is P(exactly one head | at least one head) = P(exactly one head) / P(at least one head) = (3/8) / (7/8) = 3/7. Given the phrasing, it's likely a misunderstanding or typo. Assuming the question meant 'exactly one head' and the condition is 'at least one head', the answer is 3/7.