the mean of a set of numbers can be calculated by adding all values in the set and then dividing the sum by the number of values added.
So we have:
[tex]\begin{gathered} mean=\frac{2+5+4+5}{4} \\ mean=\frac{16}{4} \\ mean=4 \end{gathered}[/tex]Therefore the mean is 4.
For the magazine set of data, we have 7 values, so the mean is:
[tex]\begin{gathered} mean=\frac{3+6+7+6+7+9+11}{7} \\ mean=\frac{49}{7} \\ mean=7 \end{gathered}[/tex]Therefore the mean is 7.