Question 1101730
 Rob is 21 years old, angie is twice as old as Rob was when Angie was old as Rob is now, how old is angie? 
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Assume the constant difference in their ages is "x".
A = 2(21-x) where A-R = x
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So, A = 42-2x
A = 42 - 2(A-R)
A = 42 - 2A + 2R
3A = 42+2(21) = 84
A = 28 yrs (Angie's age now)
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Cheers,
Stan H.
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