9 ft
1) Let's sketch that so we can better grasp it
2) Since both flagpole and you are standing on the same ground, then we can assume this is 90º and that both shadows and heights, make up similar triangles.
So applying Thales Theorem, we can write the following:
[tex]\begin{gathered} \frac{5}{20}=\frac{x}{36} \\ 20x=5\cdot36 \\ 20x\text{ =180} \\ x=\frac{180}{20} \\ x=9 \end{gathered}[/tex]
3) Hence, your shadow is 9 ft in length.
