Pls me asap for question (must show ) + lots of *brainliest *

What is the standard deviation of the following data set rounded to the nearest tenth? 3, 17, 18, 15, 12, 21, 9

Lucy is a dress maker. she sews \dfrac47 7 4 of a dress in \dfrac34 4 3 hour. lucy sews at a constant rate. at this rate, how many dresses does lucy sew in one hour? include fractions of dresses if applicable

Afrequency table of grades has five classes (a, b, c, d, f) with frequencies of 3, 13, 14, 5, and 3 respectively. using percentages, what are the relative frequencies of the five classes?