SOLUTION: In January of the year 2000, my wife lisa was eleven times as old as my son Don. In January 2012, she will be three times as old as my son. How old was my son in January of 2000?

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Question 642051: In January of the year 2000, my wife lisa was eleven times as old as my son Don. In January 2012, she will be three times as old as my son. How old was my son in January of 2000?
Answer by josmiceli(19441) About Me  (Show Source):
You can put this solution on YOUR website!
Let +x+ = Son's age in Jan 2000
Let +y+ = Lisa's age in 2000
+11x+ = Lisa's age in Jan 2000
When Son is +x+%2B+12+,
Lisa is +3%2A%28+x+%2B+12+%29+
------------------------
(1) +y+=+11x+
(2) +y+%2B+12+=+3%2A%28+x+%2B+12+%29+
------------------------
Substitute (1) into (2)
(2) +11x+%2B+12+=+3%2A%28+x+%2B+12+%29+
(2) +11x+%2B+12+=+3x+%2B+36+
(2) +11x+-+3x+=+36+-+12+
(2) +8x+=+24+
(2) +x+=+3+
and
(1) +y+=+11%2A3+
(1) +y+=+33+
Your Son was 3 in Jan 2000
check:
(2) +y+%2B+12+=+3%2A%28+x+%2B+12+%29+
(2) +33+%2B+12+=+3%2A%28+3+%2B+12+%29+
(2) +45+=+3%2A15+
(2) +45+=+45+
OK