Culegere Matematica Clasa A 9 A Better -

He had learned something the culegere never said out loud: sometimes the right answer is that there is no answer—and explaining why is the real solution.

“Easy,” Andrei muttered. Let the son be x , the father 3x . In 12 years: (3x + 12 = 2(x + 12)). He solved it: (3x + 12 = 2x + 24 \Rightarrow x = 12). Father 36, son 12. Done. culegere matematica clasa a 9 a

“The equations force the son to be 9 and the father 36, with sum 45. Since 45 is composite (3 × 15, 5 × 9), the condition ‘sum is prime’ cannot be met. Therefore, no such ages exist in whole numbers.” He had learned something the culegere never said

Andrei stared at the page. For the first time, the culegere wasn’t asking for a number. It was asking for a reason . He wrote in his notebook: In 12 years: (3x + 12 = 2(x + 12))

He checked twice. No mistake. He checked the answer key at the back—it only said “Impossible. Explain why.”