Answer:
81
Explanation:
Simple averages are......simple: add all the scores and divide by how many there are.
Add 90 & 80 & 86 & 76 and 73 to get 405
Then count up how many tests there were: 5
Now divide 405 by 5 to get the average:
405 ÷ 5 = 81
Aiko's average grade on each of those 5 tests was 81.