Solve for x
please give an explanation

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

Tamera puts 15/4 gallons of gasoline in her car. which mixed number represents the gallons of gasoline? a) 2 3/4 gallons b) 3 1/4 gallons c) 3 3/4 gallons d) 4 1/2 gallons answer it's worth a lot of points!

The ratio of rock songs to dance songs on jonathan’s mp3 player is 5: 6. the total number of rock and dance songs jonathan has is between 101 120. how many rock songs does he have?