Algebra 1

Published by Prentice Hall
ISBN 10: 0133500403
ISBN 13: 978-0-13350-040-0

Chapter 3 - Solving Inequalities - 3-6 Compound Inequalities - Lesson Check: 3

Answer

85$\leq$x$\leq$100

Work Step by Step

Let call x the next test score the person have to get in order to have average between 85 and 90 inclusively. 85$\leq$$\frac{83+87+x}{3}$ $\leq$90 => 85$\leq$$\frac{83+87+x}{3}$ and $\frac{83+87+x}{3}$$\leq$90 =>255$\leq$83+87+x and 83+87+x$\leq$270 =>255$\leq$170+x and 170+x$\leq$270 =>80$\leq$x and x$\leq$100 => 80$\leq$x$\leq$100
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