Question 1113116
 Travis is 21 years older than his sister Michelle. In 9 years, he will be twice as old as Michelle. How old is each of them now? 
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Equations:
T = M + 21
T+9 = 2(M+9)
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Substitute for "T" and solve for "M":
M+21+9 = 2M + 18
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M + 30 = 2M+18
M = 12 (Michelle's age now)
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T = M + 21 = 33 (Travis's age now)
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Cheers,
Stan H.
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