What is 3/4 of 16 help ​

Can someone me out here number 4 plz

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

Which of the following choices gives you a slope of 3?