Answer
$98.1$
Work Step by Step
Let $x=x_{2}-x_{1}$
where $x_{1}$ is the leg adjacent to $60^{o}$ in the small right triangle on the left,
and $x_{2} $ is the leg adjacent to $30^{o}$ in the large right triangle.
$\displaystyle \tan 60^{o}=\frac{85}{x_{1}}\ \Rightarrow\ x_{1}=\frac{85}{\tan 60^{o}}$
$\displaystyle \tan 30^{o}=\frac{85}{x_{2}}\ \Rightarrow\ x_{2}=\frac{85}{\tan 30^{o}}$
$ x=\displaystyle \frac{85}{\tan 30^{o}}-\frac{85}{\tan 60^{o}}\approx$98.1495457622$\approx 98.1$
