70 ≤ (85+84+67+92+x)/5 ≤ 80
350 ≤ 85+84+67+92+x ≤ 400
350 ≤ 328+x ≤ 400
22 ≤ x ≤ 72
If the 5th test count double, then you have
70 ≤ (85+84+67+92+2x)/6 ≤ 80
Now finish it off as above
In your class, you have scores of 85, 84, 67, 92 on the first four of five tests. To get a grade of C, the average of the first five test scores must be greater than or equal to 70 and less than 80.
Solve an inequality to find the least score you can get on the last test and still earn a C.
What score do you need if the fifth test counts as two tests?
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