Question 1121555
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(1)  M = S + 31    ("Sherry is 31 years younger than her mom.")
(2)  S + M = 61.   ("The sum of their ages is 61")


From (1), substitute M = S + 31  into equation (2). You will get


S + (S+31) = 61


2S + 31 = 61


2S = 61 - 31 = 30


S = 30/2 = 15.


<U>Answer</U>.  Sherry is 15 years old.
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Solved.


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