If Harry's age is exactly three times Bill's age, what is Harry's age?

We can let Harry’s age today = h and Bill’s age today = b.

Since Harry's age is exactly three times Bill's age, we know that h = 3b.

We need to determine h.

Statement One Alone:

Six years ago, Harry's age was fifteen times Bill's age. If we go back in time six years, Harry’s age was (h - 6) and Bill’s age was (b - 6). We can create the following equation:

h - 6 = 15(b - 6)

h - 6 = 15b - 90

h = 15b - 84

Since h = 3b, we have:

3b = 15b - 84

84 = 12b

b = 7

Thus, h = 3 x 7 = 21.

Statement one alone is sufficient to answer the question.

Statement Two Alone:

Seven years from now, Harry's age will be twice Bill's age. If we go forward in time seven years, Harry’s age will be (h + 7), and Bill’s age will be (b + 7). We can create the following equation:

h + 7 = 2(b + 7)

h + 7 = 2b + 14

h = 2b + 7

Since h = 3b, we have:

3b = 2b + 7

b = 7

Thus, h = 3 x 7 = 21.

Statement two alone is sufficient to answer the question.

Answer: D