Difficulty: Easy
Correct Answer: 24, 4
Explanation:
Introduction / Context:Two simultaneous linear relations (difference and multiple) uniquely determine two unknown ages. Solve by substitution or elimination.
Given Data / Assumptions:
Concept / Approach:Equate the two expressions for A to get a single equation in B, then recover A.
Step-by-Step Solution:
B + 20 = 6B ⇒ 5B = 20 ⇒ B = 4A = 6B = 24Verification / Alternative check:Check: A − B = 24 − 4 = 20 and A = 6 × 4 = 24. Both hold.
Why Other Options Are Wrong:42, 7 or 30, 5 do not satisfy both the +20 and ×6 conditions together.
Common Pitfalls:Mixing the add and multiply constraints or solving for A first and forgetting to back-substitute correctly.
Final Answer:24, 4.
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