Question 1117392
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Joe is 12 years older than Ruth.  so Joe will be twice Ruth's age when Joe will be 24 years old and Ruth will be 12 years old. 


It will happen in two years.
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It is the <U>mental solution</U>.



The <U>algebra solution</U> is as follows.


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Let x is the number of years under the question.  Then 


22 + x = 2*(10+x)

22 + x = 20 + 2x

22 - 20  = 2x - x  ====>  x = 2,  and you have the same answer.
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Solved.