The given problem describes a binomial distribution with p = 60% = 0.6. Given that there are 400 trials, i.e. n = 400.
a.) The mean is given by:

The standard deviation is given by:

b.) The mean means that in an experiment of 400 adult smokers, we expect on the average to get about 240 smokers who started smoking before turning 18 years.
c.) It would be unusual to observe <span>340 smokers who started smoking before turning 18 years old in a random sample of 400 adult smokers because 340 is far greater than the mean of the distribution.
340 is greater than 3 standard deviations from the mean of the distribution.</span>
Step-by-step explanation:
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It is four. So two and two you add them together to be four. Good job. Your learning :)
<span>add 2/9x to both sides, if you do that you get 2/9x+y=3. If you want to simplify it multiply everything by the denominator, in this case, 9 so then you would have 2x+9y=27
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Stop posting on here and do the work yourself I usually don't mind helping people but in some cases, I need to just say do it by yourself look at notes look up the answer there are a million things you can do instead of spam posting all your questions good day