Question 1175716
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From the condition, it is easy to get it mentally, that 
their current age is 14 years and 42 years.


Or, formally,  x + 3x = 56  implies the same.



Next, considering divisibility by 5, only the age of 35 does suit for the father.


<U>ANSWER</U>.  It happened 7 years ago.
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Solved.