Is my son 12 years old?
I Four years later he will be twenty years younger than me.
II. Now, I am twenty years older than him.

Explanation

This is a deceptive problem. You should notice that there are two unknowns in this case: .Father. and .Son.. But how many information.s are there? Two? No. There is only one information. Both statements I and II only state that the father is older than the son by 20 years (although the language of I and II are different). So, here, we have repetition of data Since there is one information (one equation) for two unknowns, data are insufficient and the answer is E.