Using the given information, we form the following diagram.
To find x we use Pythagorean's Theorem.
[tex]20^2=16^2+x^2[/tex]
Then, we solve for x.
[tex]\begin{gathered} 400-256=x^2 \\ x=\sqrt[]{144} \\ x=12 \end{gathered}[/tex]
Therefore, the answer is 12 feet.
