Age of grandfather = x years

age of son = x months = y days

age of father = y weeks.

x months = x/12 years.

y days = x months = x/12 years.

y weeks = 7*y days = 7*x months = 7*x/12 years.

x years + y weeks + x months or y days = 140 years.

x years + 7*x/12 years + x/12 years = 140 years.

12*x/12 years + 7*x/12 years + x/12 years = 140 years.

12x+7x+x years/12 = 140 years.

20x/12 = 140

x = 140*12/20 = 84

So, age of grandfather = 84 years.

age of son = 84 months =7 years.

age of father = 140-7-84 = 49

age of father = 49.

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