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when Mrs jones was older than 50 but younger than 80, she told a friend,
"each of my sons has as many sons as brothers, and the number of my years
is exactly that of the number of both my sons and grandsons."
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Let n be the number of her sons.
Each of the sons has (n-1) brothers.
So, to answer the problem's question, we should solve this inequality
50 < n*(n-1) + n < 80
or, equivalently,
50 < n^2 < 80,
which gives a unique solution n = 8.
So, her age is n*(n-1) + n = n^2 = 8^2 = 64. ANSWER
Solved, answered, carefully explained and completed.