Question 1143764
<br>
Here is an alternative method for solving a problem like this involving the average of numbers that are close together.<br>
Compare the given numbers to the desired average to see how far above or below the desired average the current tests are:<br><pre>
75:  -5
80:   0
70: -10
65: -15
92: +12
   -----
    -18<br></pre>
Overall, the current test scores are 18 points below the desired average; the score on the final has to make up those 18 points.  Since the final counts as two tests, the score on the final must be 18/2 = 9 points above the desired average.<br>
ANSWER: 80+9 = 89