Yo can someone help me with this please and please explain

It is given that the line plot below represents the number of letters written to overseas pen pals by the students at the Waverly middle school. Each x represents 10 students.

First of all count the number of x in the given line plot.

The total number of x in the line plot is 30. It means the total number of students is 30x = 30× x=300

From the figure, it is noticed that there are four x when the number of letters is 6 and three x where the number of letters is 20.

It means a total of 40 students wrote 6 letters and 30 students wrote 20 letters.

The number of students who wrote more than 6 but less than 20 letters is 300 - 40 - 30 = 230

answer: .64

step-by-step explanation

set up the formula for standard deviation for this set of numbers, then simplify