Difficulty: Medium
Correct Answer: 8 years
Explanation:
Introduction / Context:
Mixing a present-time difference with a past-time multiplicative relation yields a solvable two-equation system in present ages A and B.
Given Data / Assumptions:
Concept / Approach:
Substitute the expression for A from the first equation into the second and solve for B; then recover A.
Step-by-Step Solution:
Verification / Alternative check:
B two years ago = 4; 2 × 4 = 8 = A now; and A − B = 2 holds (8 − 6).
Why Other Options Are Wrong:
12, 14, 18 violate either the difference or the past-time doubling relation.
Common Pitfalls:
Doubling B now instead of B two years ago, or misapplying the 2-year difference sign.
Final Answer:
8 years.
Discussion & Comments