Answer
$554ft$
Work Step by Step
Use the figure given in the problem, assume the short side of the right triangle with $85^\circ$ has a length of $x$,
we have $tan85^\circ=\frac{h}{x}=11.430$ and $tan75^\circ=\frac{h}{x+100}=3.732$
The first equations gives $x=\frac{h}{11.430}$, use it in the second equation to get
$h=3.732\times(\frac{h}{11.430}+100)$ solve for $h$ to get $h\approx554ft$
