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Hi,
Mary's mother is 3 times as old as Mary's age
 y = 3x is mary's mother's age
Question states*** 4 yrs ago...
  x-4 = (1/4)(y-4)
  x - 4 = (1/4)(3x-4)
    (1/4)x = 3
         x = 12, Mary's age.  Mother is 36.
and... 4 yrs ago
