Question 510962
35+x = 3(9+x)
35+x = 27 + 3x
-2x = -8
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x = 4
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In 4 years, the father will be 39 and the son will be 13.  39 = 3*13.
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It is impossible for a son to be 3 times the father's age ever, so I solved it the other way.
The father will be 3 times the son's age in 4 years.
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Done.