Solution for Set 2 question 1:
Let m be the mother's age and Alvin's age be a.
As the mother is 42 - 14 = 28 years older than Alvin, m = a + 28.
At the moment m = 2a, hence 2a = a + 28, and so a = 28.
That is, Alvin is now 28 years old.
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