Answer:
See Below
Step-by-step explanation:
First off lets Let x = quiz score on Friday
We are given that Lula's mean for quiz marks is 58
We also know that her quiz marks were 67, 45, 55, and 60 for the first four days.
Given this we must create an equation so we can solve for her quiz mark on Friday.
First off, Mean = average, more specifically
Mean = sum of numbers / # of numbers
In this case, mean = sum of quiz marks for each day / number of days
If x = quiz mark on Friday than sum of quiz marks is 67 + 45 + 55 + 60 + x
If Lulu took her quiz marks from 5 days than the mean of her quiz marks is
(67 + 45 + 55 + 60 + x) / 5
We know that the mean of her quiz marks is 58
Therefore (67 + 45 + 55 + 60 + x) / 5 must equal 58
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Note that we've just created an equation that we can use to solve for x ( or quiz mark on Friday )
We now solve for x using the equation we created
(67 + 45 + 55 + 60 + x) / 5 = 58
* combine like terms *
( 227 + x ) / 5 = 58
* multiply both sides by 5
227 + x = 290
* subtract both sides by 227
x = 63
Thus, we can conclude that her quiz mark on Friday was 63
