Let the current ages of Dick, Tom, and Harry be \(D, T,\) and \(H\) respectively.
The given conditions are:
Dick is 3 times as old as Tom:
Harry is twice as old as Dick:
\[H = 2D \tag{ii}\]Dick’s age is one less than the average of their ages:
Substitute equations (i) and (ii) into equation (iii):
Simplify the numerator:
The equation becomes:
Multiply both sides by 9:
\[9D + 9 = 10D \Rightarrow 10D - 9D = 9 \Rightarrow D = 9 \tag{iv}\]Substitute \(D=9\) into equation (ii):
\[H = 2D = 2 \times 9 = 18\]Final Answer: \( \boxed{18} \) (Option D)