Since it is circular, it must fit into a square and not inyo a rectangle, therefore the maximum size oof the the backyard in the shape of a square is 50x50 feet.
If we subtract 8 from each edge, the it would be:
[tex]\begin{gathered} 50-2\cdot8 \\ 50-16=34 \end{gathered}[/tex]34 would be the diameter of the circle, therefore the radius would be:
[tex]\begin{gathered} r=\frac{d}{2} \\ r=\frac{34}{2}=17 \end{gathered}[/tex]The radius is 17 feet
