average=(sum of all scores)/(number of scores), in this case we see that:
92=s/8 so sum of the first eight test scores is:
s=8(92)=736 now we wish to know the minimum score on the next test that will result in an average of 90...
(736+s)/(8+1)\(\geq\)90 multiply both sides by 9
736+s\(\geq\)810 subtract 736 from both sides
s\(\geq\)74
Thus a score of 74 or more is necessary to maintain an average of at least 90
