A person is asked to state his age in years. He says, "Take my age three years from now, multiply it by three, then subtract three times my age three years ago, and you will get my present age." How old is the person now?

Introduction / Context:
This is an algebraic age puzzle that requires translating a verbal description into a simple equation. Such problems are common in aptitude exams because they test logical interpretation of language as well as basic linear equation solving skills.

Given Data / Assumptions:

• Let the present age of the person be A years.
• Age three years from now is A + 3.
• Age three years ago was A - 3.
• The statement says: three times age three years from now minus three times age three years ago equals the present age A.

Concept / Approach:
The strategy is to convert the verbal condition into an algebraic equation. Once we write the equation in terms of A, we can simplify it and solve for A using basic algebra. The structure of the statement sets up a linear equation with only one unknown, which is straightforward to solve.

Step-by-Step Solution:
Let the present age be A years.Age three years from now = A + 3.Age three years ago = A - 3.Given condition: 3 × (A + 3) - 3 × (A - 3) = A.Expand both products: 3(A + 3) = 3A + 9 and 3(A - 3) = 3A - 9.Substitute into the equation: (3A + 9) - (3A - 9) = A.Simplify the left side: 3A + 9 - 3A + 9 = 18.So we get 18 = A.Therefore, the present age of the person is 18 years.

Verification / Alternative check:
Check the statement using A = 18. Age three years from now: 18 + 3 = 21. Age three years ago: 18 - 3 = 15. Now compute 3 × 21 - 3 × 15 = 63 - 45 = 18, which matches the present age. The condition is satisfied exactly, confirming that 18 years is the correct solution. No other age will satisfy this specific equation.

Why Other Options Are Wrong:
If A were 20, then 3(A + 3) - 3(A - 3) would be 3 × 23 - 3 × 17 = 69 - 51 = 18, not 20. For 24, the expression gives 3 × 27 - 3 × 21 = 81 - 63 = 18 again, not 24. Similar checks for 30 or 36 show that the left side remains 18 because the A terms cancel out, so only A = 18 fulfills the required equality.

Common Pitfalls:
Some learners misinterpret the phrases three years hence and three years ago and may write A + 3 and 3 - A or mix up the direction of time. Others forget to distribute the multiplication correctly over the parentheses, leading to incorrect expansion. Careful reading of the statement and stepwise algebraic expansion help avoid such mistakes.

Final Answer:
The person is currently 18 years old.