SOLUTION: david is 12 years older than his sister, what is david's age when he is 3 times as old as his sister?

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Question 399381: david is 12 years older than his sister, what is david's age when he is 3 times as old as his sister?
Answer by ewatrrr(24785) About Me  (Show Source):
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Hi

david is 12 years older than his sister

Let x and (x+12)represent the sister and david's age respectively 

Question states***

 (x+12) = 3x

    12 = 2x

     x = 6, the sister's age.  David is 18.



CHECKING our Answer***

  18 = 3*6