Question 1771: Robert is 14 years old and his father is 38 years old. How many years ago was the father exactly seven time as old as his son?
Answer by longjonsilver(2297)   (Show Source):
You can put this solution on YOUR website! this is a good question:-)
The one bit of information they want is "when was the father x7 as old as his son." so, in algebraic terms, this is "when is f=7r" where f is the father and r is robert. Or, 
What we do know is that now, we have 38/14, which is NOT 7. Last year, we had 37/13, 2 years ago we had 36/12, 3 years ago we had 35/11 and "n" years ago we had  and here we want this to be 7.
So, we just solve 
You do the solving. Answer is n=10, ie ten years ago (when father was 28 and son was 4).
cheers
Jon.
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