Question

I'm not sure how to do this. Can anyone help me solve it correctly?

On the past two quizzes, a student scored a 75 and 83. Write and solve a compound inequality to find the possible values for the 3rd quiz score that would get her an average between 85 and 90, inclusive.

Answer 1

Ok I got 91<=x<=101
Is this correct?

Answer 2

the total points for the 3 tests is 3 times the average, so we need
3*85 <= 75+83+x <= 3*90
255 <= 158+x <= 270
97 <= x <= 112

So, only a 97,98,99 or 100 will raise her average that much.

Answer 3

Thank you Steve!