Question 1117658
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Let x be the sister age.

Then the mom's age is 3x, according to the condition.


In 12 years the sister will be x+12 years old, while the mom will be 3x+12,

and the condition says that then


2*(x+12) = 3x + 12.


Simplify and solve:


2x + 24 = 3x + 12

24 - 12 = 3x - 2x  ====>  x = 12.


<U>Answer</U>.  The sister is 12 years old;  the mother's age is 3*12 = 36 years.
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