Answer
$ 40\ yards$
Work Step by Step
Step 1. Use the figure given and rewrite the equation as $\frac{y^2}{400}-\frac{x^2}{625}=1$. We have $a=20, b=25$ with center at $(0,0)$ and a vertical transverse axis.
Step 2. At the closest point, the distance between the houses is given by $2a=40\ yards$
