Answer
See below.
Work Step by Step
Let $x$ be the third grade.
a) Then $\frac{86+88+x}{3}\geq90\\86+88+x\geq270\\x\geq96$
b) Then $\frac{86+88+x}{3}\lt80\\86+88+x\lt240\\x\lt66$
Thinking Mathematically (6th Edition)
by Blitzer, Robert F.
Published by
Pearson
ISBN 10:
0321867327
ISBN 13:
978-0-32186-732-2
Chapter 6 - Algebra: Equations and Inequalities - 6.4 Linear Inequalities in One Variable - Exercise Set 6.4 - Page 385: 87
Update this answer!
You can help us out by revising, improving and updating this answer.
Update this answerAfter you claim an answer you’ll have 24 hours to send in a draft. An editor will review the submission and either publish your submission or provide feedback.
