Sandsynlighedsregning

Hej

Jeg har svært ved fælgende opgave:

"A recent study found that 172 out of 1000 male smokers will eventually develop lung cancer, while only 13 out of 1000 males will develop lung cancer among the nonsmokers. Among the male population in which the study was conducted, 30% are smokers. What is the probability that a male patient diagnosed with lung cancer is not a smoker?"

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