The mean of a set of data can be found through the formula
[tex]\bar{x}=\frac{\sum ^n_{i\mathop=0}x_i}{n}[/tex]
then, the mean water level can be found as
[tex]\begin{gathered} \bar{x}=\frac{7+2+8+7+2+8+6+5+9}{9} \\ \bar{x}=\frac{54}{9} \\ \bar{x}=6 \end{gathered}[/tex]
