Answer:
6 units
Step-by-step explanation:
Gravitational force between two objects is given by the equation

where
universal gravitational constant
,
are the masses of the objects
= distance between the objects
We are given that F = 18 units.
If m₁ is tripled and r is also tripled then
new F = F':


Therefore the new F is 1/3 of the old f
In this case that would be 18/3 = 6 units