Using the mean concept, it is found that he needs to sell at least 76 copies this month to maintain average of at least 75 sales per month.
The mean of a data-set is given by the sum of all observations in the data-set divided by the number of observations.
In this problem, there are 5 observations, given as follows:
82, 29, 109, 79 and x.
In which x is the number of copies sold this month.
The average is of at least 75, hence:
(82 + 29 + 109 + 79 + x)/5 = 75
299 + x = 75 x 5
x = 375 - 299
x = 76.
He needs to sell at least 76 copies this month to maintain average of at least 75 sales per month.
More can be learned about the mean of a data-set at https://brainly.com/question/24628525
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