If the change in the value of ‘g’ at a height h above the surface of the earth is the same as at a depth x below it, then (both x and h being much smaller than the radius of the earth):

x = h x = 2 h x = 1/2 h x = h2

x = 2 h

$g\left(1-\frac{x}{R}\right)=g\left(1-\frac{2 h}{R}\right)$ $\Rightarrow \frac{x}{R}=\frac{2 h}{R} \Rightarrow \frac{x}{h}=2$