Answer:
Michelle must get an 80 on her next test to keep her average score.
Explanation:
Since Michelle got an average score of 80 on two tests, to determine what score she must get on the third test so that her average score for the three tests is the same as the average score for the first two tests, the following calculation must be performed:
X / 2 = 80
X = 80 x 2
X = 160
X x 3 = 80 x 3
X x 3 = 240
X = 240/3
x = 80
So, Michelle must get an 80 on her next test to keep her average score.