According to the plot, it looks like [tex]y=3.5[/tex] when [tex]x=4[/tex], and [tex]y=7[/tex] when [tex]x=5[/tex]. Then the average rate of change from [tex]x=4[/tex] to [tex]x=5[/tex] is
[tex]\dfrac{\Delta y}{\Delta x} = \dfrac{7 - 3.5}{5 - 4} = 3.5[/tex]
