Question 832899
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Joe is twice as old as David. 
The sum of their ages is 63. 
How old are David and Joe
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Equations:
j = 2d
j+d = 63
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Substitute for "j" and solve for "d":
2d + d = 63
3d = 63
David = 21 years
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Solve for "j":
j = 2d
Joe = 2*21 = 42 years
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Cheers,
Stan H.
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