Finding Equilibrium: Solving a Black Hole Parking Problem

[kmcshane386]

Consider two black holes: the left one has a mass M1= 5x10^30 kg, and the right one has a mass of M2= 9x10^30 kg, and they are a distance d= 3.0x10^6 m apart. A spaceship passing between them is having engine trouble and so the captain has to park the ship somewhere where he won't get sucked into either black hole. So question is, what is the distance x the he must park away from the left black hole so that the net gravitational force due to both black holes on his ship is 0.

Equations: M3= mass of spaceship
G(M1)(M3)/x^2 + G(M2)(M3)/d-x^2=0



(6.67x10^-11(5x10^30)(M3)/x^2) + (6.67x10^-11(9x10^30)(M3)/d-x^2)

How do I find the mass of the spaceship? I feel like I'm missing a variable...

 

[Fightfish]

Why do u need the mass of the spaceship?

Also, why is your equation for equilibrium
G(M1)(M3)/x^2 + G(M2)(M3)/d-x^2=0 ?

The sum of two strictly positive quantities cannot be zero.