Question 1115618
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Let x be the Nick's age.


Then the Sarah age is 3x, according to the condition.


Also, the condition says that 


    3x - x = 28,


which implies  2x = 28  and  x = 14.


<U>Answer</U>.  Nick is 14 years old.  Sarah is 3*14 = 42 years old.
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Solved.