Question 1043506
Average score=total/n
n is 7, five tests taken and 2 that are counted for the final
Average is 80.
Therefore, 80=total/7
Total=560.
Now, add up the 5 results you know: to get 388
She needs a total of 172 points on the final to make 560.
The final counts twice, so the scores are equal.  172/2=86.
She needs an 86.
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Does it make sense?
She was minus 3, plus 4, minus 8, minus 17 and plus 12 from 80 on her 5 tests.  That is minus 12.
She needs a score greater than 80, and if she gets an 86, that is plus 6 twice, which cancels out the minus 12, so 86 is confirmed.