A student scored 81 and 95 on her first two quizzes. Write and solve a compound inequality to find the possible

values for a third quiz score that would give her an average between 85 and 90.

1 answer

85<((81+95+x)/3)<90.
85<((176+x)/3)<90
Multiply by 3:
255<(176+x)<270
Subtract 176:
79<X<94.

Third quiz between 79 and 94.