How old is Jack?
I. After 20 years, Jack will be twice as old as he is today.
II. Five years ago, Jack was ¾ times of his present age.
Let Jack’s current age be x years, From I, x + 20 = 2x x = 20 From II, x – 5 = ¾ x 4x – 20 = 3x x = 20 Thus, either of statements alone is sufficient to answer the given question.