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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Question 148535: 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 score..
Answer by jim_thompson5910(35256) About Me  (Show Source):
You can put this solution on YOUR website!

Let x=score on fourth exam

So the average A of all 4 exams are
75, 79, and 81
A=%2875%2B79%2B81%2Bx%29%2F4


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

%2875%2B79%2B81%2Bx%29%2F4%3E=80 Set the right side greater than 80


75%2B79%2B81%2Bx%3E=320 Multiply both sides by 4.


x%2B235%3E=320 Combine like terms on the left side.


x%3E=320-235 Subtract 235 from both sides.


x%3E=85 Combine like terms on the right side.


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Answer:

So the answer is x%3E=85 which means that the student must get an 85 or better on the 4th exam.