SOLUTION: Two years ago john was 7 times as old as his son but in 3 years he wil be 4 times as old as the boy. How old is john?

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Question 1035214: Two years ago john was 7 times as old as his son but in 3 years he wil be 4 times as old as the boy. How old is john?
Answer by josmiceli(19441) About Me  (Show Source):
You can put this solution on YOUR website!
Let +j+ = John's age now
Let +s+ = son's age now
-------------------------
(1) +j+-+2+=+7%2A%28+s+-+2+%29+
(2) +j+%2B+3+=+4%2A%28+s+%2B+3+%29+
-----------------------
(1) +j+-+2+=+7s+-+14+
(2) +j+%2B+3+=+4s+%2B+12+
-----------------------
(1) +j+-+7s+=+-12+
(2) +j+-+4s+=+9+
---------------------
Subtract (1) from (2)
(2) +j+-+4s+=+9+
(1) +-j+%2B+7s+=+12+
-------------------
+3s+=+21+
+s+=+7+
and
(1) +j+-+2+=+7%2A%28+s+-+2+%29+
(1) +j+-+2+=+7%2A%28+7+-+2+%29+
(1) +j+-+2+=+7%2A5+
(1) +j+=+35+%2B+2+
(1) +j+=+37+
John is 37
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check:
(1) +j+-+2+=+7%2A%28+s+-+2+%29+
(1) +37+-+2+=+7%2A%28+7+-+2+%29+
(1) +35+=+7%2A5+
(1) +35+=+35+
OK
(2) +j+%2B+3+=+4%2A%28+s+%2B+3+%29+
(2) +37+%2B+3+=+4%2A%28+7+%2B+3+%29+
(2) +40+=+4%2A10+
(2) +40+=+40+
OK