Question 429574
Darren is three years older than his sister.In three years, he will be twice as old as she will be then.How old is each now? 

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Let Darren be "d" now.
Let Sister be "s" now.
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Equations:
d = s + 3
(d+3) = 2(s+3)
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Substitute for "d" and solve for "s":
(s+3+3) = 2(s+3)
s+6 = 2s+6
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s = 0 (sister's age now)
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d = s+3
d = 3 yrs old (Darren's age now)
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Cheers,
Stan H.
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