Answer
$d=4767~ft$
Work Step by Step
Let $\theta$ be the angle between $d$, the hypotenuse, and the vertical side of the right triangle:
$\theta=90°-39°=51°$
$cos~\theta=\frac{adj}{hyp}$
$cos~51°=\frac{3000}{d}$
$d=\frac{3000}{cos~51°}\approx4767$
