2. Mary's test average after 8 tests is 80. Her score on the
9th test was 71. If all 9 tests are weighted equally, what
is Mary's test average for all 9 tests?
A. 71
B. 75.5
C. 77
D. 79
E. 80
since her test average for the first 8 tests is 80, the sum of all the scores for the first 8 tests is 640. Since her 9th test is 71, we do 640+71=711. To find the average of all 9 tests, we do 711/9 = 79
