At what distance from the Earth and the moon have zero net force?

[Gardalay]

Homework Statement

At what distance from the Earth will a spacecraft traveling directly from the Earth to the Moon experience zero net force because the Earth and Moon pull with equal and opposite forces?

Homework Equations

GM(earth)/(R-d)^2=GM(moon)/d^2

The Attempt at a Solution

Me/Mm=81.3
root 81.3=(R-d)/d

I have no idea how to figure out the rest of the question. Please help.

 

[rock.freak667]

(a-b)/c = a/c - b/c

use this and solve

 

[rock.freak667]

(a-b)/c = a/c - b/c

use this and solve