Question 1196293
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x = score on the exam
2x = equivalent score on a quiz (since the exam counts for two quizzes)
For instance if you got an 82 on the exam, then it is equivalent to 2*82 = 164 points for a quiz. 
It might be helpful to think of it like getting 82's on two different extra quizzes.


It also might be helpful to think of the 2x as x+x
So that we can break things further down


A = set of scores
A = {87, 89, 88, 78, x, x}
Note I listed x twice
There are 6 elements in set A


Now compute the average. Do so by adding up the scores and dividing by the number of scores (6)
So we get:
(87+89+88+78+x+x)/6
which simplifies to 
(342+2x)/6


Set this average equal to the target 85 and solve for x.
(342+2x)/6 = 85
342+2x = 6*85
342+2x = 510
2x = 510-342
2x = 168
x = 168/2
x = 84


Answer: <font color=red>84</font>
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