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原帖由 ChARsoN 於 2008-12-11 19:00 發表
Let x be the age of the son
Let y be the age of the mother
y - x = 21 --------(1)
y + 6 = 5(x+6) ---------(2)
Fm. (1), y = 21 + x ----------(3)
Sub. (3) into (2) : 21 + x + 6 = 5(x + 6)
27 + x = ...
師兄,好老實講,小弟只睇你呢堆野,就發現小弟真係冇乜IQ,所以小弟可以好放心繼續跑步,唔驚冇晒IQ啦!反正都冇! |
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