SOLUTION: justin earns scores of 75,83,77,and 81 on his first four exams in math class. the final exam is worth twice a regular exam(twice the weight). he wants to earn a B, so he needs at l

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Question 165667: justin earns scores of 75,83,77,and 81 on his first four exams in math class. the final exam is worth twice a regular exam(twice the weight). he wants to earn a B, so he needs at least an 80 average. solve the following equation to find the lowest score he can earn and still get his B!
(75+83+77+81+2x) /6 =80

I must show my work and i don't know how ???? please help me !!!!!
Found 2 solutions by jim_thompson5910, stanbon:
Answer by jim_thompson5910(35256) About Me  (Show Source):
You can put this solution on YOUR website!
%2875%2B83%2B77%2B81%2B2x%29%2F6+=80+ Start with the given equation


%28316%2B2x%29%2F6+=80+ Combine like terms.


cross%286%29%28%28316%2B2x%29%2Fcross%286%29%29+=80%286%29+ Multiply both sides by 6


316%2B2x=480 Multiply


2x=480-316 Subtract 316 from both sides.


2x=164 Combine like terms on the right side.


x=%28164%29%2F%282%29 Divide both sides by 2 to isolate x.


x=82 Reduce.


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Answer:

So the answer is x=82 which means that he must an 82 or better to get an average of 80 or better.

Answer by stanbon(75887) About Me  (Show Source):
You can put this solution on YOUR website!
(75+83+77+81+2x) /6 >=80
Multiply both sides by 6 to get:
316 + 2x >= 480
2x >= 164
x >= 82
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Chers,
Stan H.