Answer:
Mary's age = 36
Son's age = 12
Explanation:
Let x be age of Mary and y be age of her son.
According to question,
x = 3y...........(1)
And,
x + 12 = 2(y + 12)
x + 12 = 2y + 24
Replacing value of x from (1),
3y + 12 = 2y + 24
3y - 2y = 24 - 12
y = 12
And x = 3 x 12 = 36