Answer
$x^2=60y$
Work Step by Step
Standard form of a parabola is given as: $x^2=4py$ ...(1)
Formula to find focus is: $F(0,p)$ and formula to find directrix is: $y=-p$ or, $y+p=0$
As we are given that focus is: $(0,15)$ and directrix is: $y=-15$ or $x+15=0$
Plug all these data in equation (1), we have: $p=15$
Thus, $x^2=4(15)y \implies x^2=60y$