Explain how you can use mental math to perform the following addition

Which of the following is the result of expanding

Find the solution on the interval [0, 2pi)

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. how many students wrote more than 6 and fewer than 20 letters. a.250 b.240 c.230 d.220