Question

The line plots show the number of hours two different age groups of teenagers spent online the previous week.

Answer 1

The range of the top plot, hours spent by 13-15 year olds, is found by subtracting the highest value, 34, and the lowest value, 21.  34-21=13.
The mean of the top plot is found by adding together all of the data points and dividing by 10 (the number of data points):
$\frac{21+24+26+27+27+28+28+28+31+34}{10}=\frac{274}{10}=27.4$

The range of the bottom plot, minutes spent online by 16-18 year olds, is found by subtracting the highest value, 36, and the lowest value, 12.  36-12=24.
The mean of the bottom plot is found by adding together all of the data points and dividing by 11 (the number of data points):
$\frac{12+21+27+28+28+28+28+30.5+34+35+36}{11}=\frac{307.5}{11} \approx27.95$