Object A experiences a gravitational force due to object B. How would that force change if the separation distance is halved, mA triples, and mB is reduced to one quarter of its original value?

Answer 1

You know that

F = GMm/r^2

so, what happens to F if r is replaced by r/2?

F' = GMm/(r/2)^2 = 4GMm/r^2 = 4F

use the same technique when replacing the other quantities.