SOLUTION: father's age was three times to his son's age. After 20 years it becomes two times. What is the age of son now?

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Question 502462: father's age was three times to his son's age. After 20 years it becomes two times. What is the age of son now?
Answer by josmiceli(19441) About Me  (Show Source):
You can put this solution on YOUR website!
Let f = father's age now
Let s = Son's age now
given:
(1) +f+=+3s+
(2) +f+%2B+20+=+2%2A%28+s+%2B+20+%29+
---------------------
(2) +f+%2B+20+=+2s+%2B+40+
(2) +f+-+2s+=+20+
Substitute (1) into (2)
(2) +3s+-+2s+=+20+
(2) +s+=+20+
The Son is now 20
check:
(1) +f+=+3s+
(1) +f+=+3%2A20+
+f+=+60+
and
(2) +f+%2B+20+=+2%2A%28+s+%2B+20+%29+
(2) +60+%2B+20+=+2%2A%28+20+%2B+20+%29+
(2) +80+=+2%2A40+
(2) +80+=+80+
OK