SOLUTION: 18 yrs ago, a father was 3 times as old as his son. now the fathr is only twice as old as his son. then the sum of the present ages of the son and the father

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Question 402864: 18 yrs ago, a father was 3 times as old as his son. now the fathr is only twice as old as his son. then the sum of the present ages of the son and the father
Answer by josmiceli(19441) About Me  (Show Source):
You can put this solution on YOUR website!
f = Father's age now
s = Son's age now
given:
f+-+18+=+3%2A%28s+-+18%29
f+-+18+=+3s+-+54
3s+-+f+=+36
and
f+=+2s
----------
By substitution:
3s+-+2s+=+36
s+=+36
and
f+=+2s
f+=+72
36+%2B+72+=+108
The sum of their ages now is 108
check answer:
f+-+18+=+3%2A%28s+-+18%29
72+-+18+=+3%2A%2836+-+18%29
54+=+3%2A18
54+=+54