You need to understand that you're solving for the average, which you already know: 90.
Since you know the values of the first three exams, and you know what your final value needs to be, just set up the problem like you would any time you're averaging something.
Solving for the average is simple
<h3>What is the average?</h3>
Add up all of the exam scores and divide that number by the number of exams you took.
(87 + 88 + 92) / 3 = your average if you didn't count that fourth exam.
Since you know you have that fourth exam, just substitute it into the total value as an unknown, X
(87 + 88 + 92 + X) / 4 = 90
Now you need to solve for X, the unknown
87+88+92+X4 /(4) = 90/ (4)
Multiplying for four on each side cancels out the fraction.
So now you have
87 + 88 + 92 + X = 360
This can be simplified as
267 + X = 360
Negating the 267 on each side will isolate the X value, and give you your final answer
X = 93
Now that you have an answer, ask yourself does it make sense.
I say that it does because there were two tests that were below average, and one that was just slightly above average.
To learn more about the average visit:
brainly.com/question/10428039
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