We have a circle with radius (r) 8m and an angle (let's call it theta) of 140°, so:
[tex]\begin{gathered} r\text{ = 8} \\ \theta\text{ = 140\degree} \end{gathered}[/tex]Now, the arc is given by:
[tex]arc(AB)=r\cdot\theta^{}[/tex]But , theta must be in radians!
So, all you need to do is to express theta in radians and replace in the previous equation.
To do