Let x be the mean (in points) of three test scores, x1, x2, and x3, all in

Question:

Let x be the mean (in points) of three test scores, x1, x2, and x3, all in points.
a. Find a formula for the mean of the test scores.
b. If a student has test scores of 72 and 85, find the score she needs on the third test so that her three-test mean score is 80 points, which is the cutoff for a B.