Question 1771
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, {{{(f/r)=7}}}

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 {{{(38-n)/(14-n)}}} and here we want this to be 7.

So, we just solve {{{(38-n)/(14-n) = 7}}}

You do the solving. Answer is n=10, ie ten years ago (when father was 28 and son was 4).

cheers
Jon.