Step-by-step explanation:
It is given that,
Speed of Anna is x miles/hour
Speed of Sara is 10 mi/h
We need to find an expression that represents the average of Anna's and Sara's speeds. Average of two objects is given by :
[tex]v=\dfrac{v_1+v_2}{2}[/tex]
ATQ,
[tex]v=\dfrac{x+10}{2}[/tex]
The above expression represents the average speed of Anna and Sara.