Question 976272
I found the clumsy English translation challenging, so I "googled" the phrase
"son father and grandfather add up to 140 years" and found an understandableversion of the question, which had been previously asked in algebra.com:
 
Question 702668:
One grandfather
One father 
One grandson
The 3 together are 140 years old
The grandfather's age is equal to the number of months of the grandson
The father's age in weeks is equivalent to the grandsons age in days 
Tell me what are the individual ages of the 3?
 
MY SOLUTION (which agrees with the two solutions to Question 702668):
{{{x}} age of the grandson (in years)
Since "the grandfather's age is equal to the number of months of the grandson",
{{{12x}}}= age of the grandfather (in years).
Since "fhe father's age in weeks is equivalent to the grandsons age in days",
{{{7x}}}= age of the father.Then,
{{{x+12x+7x=140}}}= sum of their ages (in years).
So we solve:
{{{x+12x+7x=140}}}
{{{20x=140}}}
{{{x=140/20=highlight(7)}}}
{{{7x=7*7=highlight(49)}}}
{{{12x=12*7=highlight(84)}}}
 
NOTES: Question 702668 was posted around 1/16/2013. My search showed there were other similar postings in other websites.