Question

a student scored 78 and 95 on his first two quizzes. Use a compound inequality to find the possible values for a third quiz score that would give him an average between 80 and 90

Answer 1

He gets an average between 80 and 90
 It is between these two values
 So it could be 80 or higher but it must be 90 or belowe so it can be equal to 80 or above and it can be equal to 90 or below
 This gives two inequalities 80 ≤ x and x ≤ 90
 This can be written as 1 inequality 80 ≤ x ≤ 90
 ≤ this means less than or equal to the one that points the opposite way would be greater than or equal to think of it as a number line pointing right is positive meaning the numbers get bigger, getting greater pointing left is getting smaller so it gets less and less