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For part B.
You were on the right track in your original answer for part b and I'm not sure where you've gone with your second attempt. "What is the probability that three randomly selected Americans do not exercise regularly."
You have three events there. Each of which has a probability of 0.8 of happening. So, the chance of the first one being a non-exerciser: 0.8. The same for the second. The same for the third.
0.8 0.8 0.8
You need to multiply those and I think you knew that. However, 0.8x0.8x0.8 is not the same as 0.8x3, which is what you did.
Consider the difference between 2x3 and 2x2x2.
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As for your new question, assuming that 0.47 is the correct probability then you essentially have the exact same question as Part B.
What are the odds of the first person being a birthday drinker?
What are the odds of the second person not being a birthday drinker?
What are the odds of the third person being a birthday drinker?
Since you need to know the odds of all three things happening together, you multiply those odds.
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