The force due to gravity between two objects can be described using the equation fg = g m1 m2 / d2. according to this equation, if the distance between two objects increases, what happens to the gravitational force between them?

If the distance between the two object increases, then the force between them decreases.
In fact, the formula is

we can see that the distance d is at the denominator, therefore when d increases, the value of the fraction decreases, and so the gravitational force F decreases as well.

The answer is a 0.64 volts