Let be the mean (in points) of five test scores, x1, x2, x3, x4, and x5,

Question:

Let be the mean (in points) of five test scores, x1, x2, x3, x4, and x5, all in points.
a. Write a formula for the mean of the test scores.
b. Solve the formula you found in part (a) for x.
c. If a student has test scores of 71, 75, 88, and 81, all in points, use the formula you found in part (b) to find the score he needs on the fifth test so that his five-test mean is 80 points, which is the cutoff for a B.