A person was asked to state his age in years. He replied: Take my age 3 years from now, multiply it by 3, then subtract 3 times my age 3 years ago, and the result will equal my present age. How old is this person now?

Introduction / Context:
This is a classic age puzzle that tests your ability to translate a verbal description into an algebraic equation. Once the equation is formed, solving it is straightforward. Such puzzles frequently appear in aptitude exams to evaluate logical thinking and algebra skills.

Given Data / Assumptions:

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

Concept / Approach:
We convert the language into an algebraic equation. Then we simplify the equation and solve for A. As the numbers are small and linear, it is a simple equation in one variable.

Step-by-Step Solution:
Step 1: Assume present age = A years. Step 2: Age 3 years from now = A + 3. Step 3: Age 3 years ago = A - 3. Step 4: According to the condition: 3 × (A + 3) - 3 × (A - 3) = A. Step 5: Expand the left side: 3A + 9 - (3A - 9) = A. Step 6: Simplify: 3A + 9 - 3A + 9 = A, so 18 = A. Step 7: Therefore, the present age of the person is 18 years.

Verification / Alternative check:
Check the condition with A = 18. Age 3 years from now: 21. Age 3 years ago: 15.
3 × 21 = 63 and 3 × 15 = 45. The difference is 63 - 45 = 18, which equals the present age. This confirms the solution.

Why Other Options Are Wrong:
20: If A = 20, the calculation would give 3 × 23 - 3 × 17 = 69 - 51 = 18, not 20.
24: If A = 24, 3 × 27 - 3 × 21 = 81 - 63 = 18, not 24.
30: If A = 30, 3 × 33 - 3 × 27 = 99 - 81 = 18, not 30.
22: Similarly gives a result different from 22. Only 18 satisfies the equation.

Common Pitfalls:
The main difficulty is correctly interpreting the verbal description. Some learners may forget the negative sign when subtracting 3 × (A - 3) or may misread the phrase "3 years ago." Writing each step of the equation explicitly and expanding carefully prevents sign errors.

Final Answer:
The person is currently 18 years old.