Answer:
F=GMm/r^2 where G is the newtonian grav cst, M the mass of the star, m the mass of the planet, and r the planet-star distance
F1=GMm1/r1^2
F2=GMm2/r^2
F2/F1 = [GMm2/r2^2]/[GMm1/r1^2]
F2/F1=(m2/m1)(r1/r2)^2 = (2)(1/2)^2 = 1/2
because m2/m1=2 and r2/r1=2