So in that equation, let’s say mass 1 is earth. G and distance will be equal in both instances of dropping.

Rewrite equation:

Distance^2/ G*mass 1 = mass 2 /force

And

Distance^2/ G*mass 1 = mass 3 /force

Therefore,

Mass 2 /force = mass 3 /force

F = m*a

Mass 2 / mass 2*a = mass 3 / mass 3 * a

This cancels out to show that a = a, their acceleration is the same.