Question 572864
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The sum of the scores of the 5 tests has to be 5 times the desired average.  5 times 75 is 375.  The sum of the first 4 scores is 298.  Subtract that from 375 to get 77.


You were actually on the right track:


*[tex \LARGE \ \ \ \ \ \ \ \ \ \ \frac{73\ +\ 71\ +\ 79\ +\ 75\ +\ x}{5}\ =\ 75]


is correct.  At this point, I would have multiplied both sides by 5 to get rid of that pesky denominator, but there is really nothing wrong with your next step though.


*[tex \LARGE \ \ \ \ \ \ \ \ \ \ \frac{298\ +\ x}{5}\ =\ 75]


is also correct, as is:


*[tex \LARGE \ \ \ \ \ \ \ \ \ \ 59.6\ +\ \frac{x}{5}\ =\ 75]


and


*[tex \LARGE \ \ \ \ \ \ \ \ \ \ \frac{x}{5}\ =\ 75\ -\ 59.6]


But right here is where you made your error.  You were already dividing by 5 in the LHS, but then you chose to divide by 5 on the right (???).


*[tex \LARGE \ \ \ \ \ \ \ \ \ \ x\ \neq\ \frac{75\ -\ 59.6}{5}]


what you wanted to do was multiply both sides by 5 to get:


*[tex \LARGE \ \ \ \ \ \ \ \ \ \ x\ =\ 5(75\ -\ 59.6)\ =\ 77]

 
John
*[tex \LARGE e^{i\pi} + 1 = 0]
My calculator said it, I believe it, that settles it
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