#### Answer

$r=\frac{L}{\theta}$

#### Work Step by Step

Since the figure containing $L$, $r$ and $\theta$ represents a sector of a circle, $L$ is therefore equal to the arc length.
The general formula for arc length $s$ of a sector of a circle is $s=r\theta$. Since $L$ is equal to $s$, this formula can be written as $L=r\theta$.
Solving for $r$, the formula becomes $r=\frac{L}{\theta}$.