SOLUTION: A student has scores of 75, 79, and 81 on three government exams. What score does she need on a fourth exam to give her an average of 80 or better. Let x represent the fourth test

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Let x=score on fourth exam

So the average A of all 4 exams are
75, 79, and 81



Since the average must be greater than or equal to 80, this means that the right side is greater than or equal to 80

Set the right side greater than 80


Multiply both sides by 4.


Combine like terms on the left side.


Subtract from both sides.


Combine like terms on the right side.


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Answer:

So the answer is which means that the student must get an 85 or better on the 4th exam.