Question 1076404
That's in the same excellent RotthauserC solution here: https://www.algebra.com/algebra/homework/Probability-and-statistics/Probability-and-statistics.faq.question.1060679.html
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And... I think that's your two for the day ;-).  Do try using a search engine (I recommend DuckDuckGo.com since they don't track you) with your question and then site:algebra.com.  Your instructor seems to be using a standard base and I'm betting that you will be able to find step by step answers for many of your questions.