It is given that A: B is 1: 2.
Statement I: The ratio of ages of B and C is the duplicate of the inverse ratio of the ages of A and B. So ratio of B and C is 4: 1. Since nothing is given about D, so it is not sufficient.
Statement II: The ratio of the ages of C and D is the triplicate of the sub duplicate ratio of ages of C and B. Since the ratio of the ages of B and C is not given here, so we cannot find the oldest person.
Combining both the statements, we get B: C is 4: 1, C: D is 1: 8 and also A: B is 1: 2. So A: B: C: D is 2: 4: 1: 8. Hence the question can be solved by using both the statemnets together.