Ages (parents' age difference via birth offsets): Nisha's father was 38 when she was born. Her mother was 36 when Nisha's brother (four years younger than Nisha) was born. Find the difference in the parents' ages.

Introduction / Context:
Parent–child birth offsets allow us to infer absolute parent-age differences without knowing current ages. We align the two birth events to the same child's birth by adjusting for the sibling gap.

Given Data / Assumptions:

• Father's age at Nisha's birth = 38.
• Mother's age at her son's birth (who is 4 years younger than Nisha) = 36 ⇒ mother's age at Nisha's birth was 36 − 4 = 32.

Concept / Approach:
Compute the parents' ages at one common event (Nisha's birth) and subtract to get the permanent age difference.

Step-by-Step Solution:

Verification / Alternative check:
Age differences between parents remain constant over time; hence 6 years is valid today and at all times.

Why Other Options Are Wrong:
They reflect misadjusting the 4-year sibling gap or confusing which birth corresponds to which parent's stated age.

Common Pitfalls:
Subtracting 36 from 38 directly without aligning both to the same child's birth event.

Final Answer:
6 years