Question 1178853
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Here is an alternative method for solving this kind of average problem if the numbers are all close together.  I think it's easier because the numbers you need to work with are smaller....<br>
Compared to the desired average of 90...
96 is +6
98 is +8
86 is -4<br>
Together those three scores are 6+8-4=+10.<br>
So the score on the fourth test must be -10.<br>
ANSWER: 90-10 = 80<br>