SOLUTION: Sixteen-year old Michael is twice as old as his sister.How many years ago was he three times as old as his sister?

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Question 480518: Sixteen-year old Michael is twice as old as his sister.How many years ago was he three times as old as his sister?
Answer by Tatiana_Stebko(1539) About Me  (Show Source):
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Now Michael is 16, he is twice as old as his sister, so his sister now is 16%2F2=8 years old.
Let x years ago Michael was three times as old as his sister, Mickael's age x years ago was %2816-x%29, his sister age was %288-x%29
%2816-x%29%2F3=8-xmultiply by 3
16-x=3%288-x%29
16-x=24-3x
-x%2B3x=24-16
2x=8
x=4 years ago Michael was three times as old as his sister