Here, we have a right triangle with a missing side length.
To determine the length of the missing side, apply pythagorean theorem

Where:
c is the longest side (hypotenuse) = 20
a = 16
Substitute values into the equation and solve for the missing side.
We have:

Subtract 256 from both sides:

Take the square root of both sides:
![\begin{gathered} \sqrt[]{144}=\sqrt[]{x^2} \\ \\ 12=x \\ \\ x=12 \end{gathered}](https://img.qammunity.org/2023/formulas/mathematics/high-school/xn2jhtw4la1y1kn6pok7fpgr52ryvbh45s.png)
Therefore, the missing length is 12 units
ANSWER:
x = 12