What is 21,678 rounded to the nearest ten

You are constructing a histogram for scores that range from 70 to 100 in whole points. frequencies range from 3 to 10; that is, every whole-point score between 60 and 100 occurs at least 3 times, and at least one score occurs 10 times. which of these would probably be the best range and size for the score intervals along the x-axis?

What is the measure of ac? 5 units 13 units 26 units 39 units

Which inequality comparing two of the expressions is true when 0.7 < x < 0.9