Answer:
A score of greater than equal to 128 and less than 188 will get a grade of Upper C
Step-by-step explanation:
We are given the following in the question:
Scores:
66, 74, 71, 81
Let x be the score on fifth test.
To get a grade of Upper C, the average of the first five tests scores must be greater than or equal to 70 and less than 80.
The fifth test counts as two tests.
Putting the values we get:
Thus, a score of greater than equal to 128 and less than 188 will get a grade of Upper C