A man’s age after 15 years will be four times his age 15 years ago. What is his present age?

Introduction / Context:
This is a symmetric past–future linear relationship around the present age. Convert directly to a single linear equation in the present age x and solve.

Given Data / Assumptions:

• Let present age = x years
• x + 15 = 4(x − 15)

Concept / Approach:
Expand, collect like terms, and isolate x; ensure the result is a realistic positive age.

Step-by-Step Solution:

Verification / Alternative check:
15 years ago: 10; in 15 years: 40 ⇒ 40 = 4 × 10, as required.

Why Other Options Are Wrong:
10, 15, 20 do not satisfy the equation x + 15 = 4(x − 15).

Common Pitfalls:
Using 4x = x + 30 (incorrect) or forgetting to distribute 4 across both terms in (x − 15).

Final Answer:
25 yr.