We will have the following:
We will determine the missing values as follows:
[tex]\begin{gathered} 75=\frac{71+72+73+74+75+76+77+78+x}{9}\Rightarrow75=\frac{596+x}{9} \\ \\ \Rightarrow675=596+x\Rightarrow x=79 \end{gathered}[/tex]So, the missing value must be 79.
