Question 1119685
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The difference 73 - 58   is  15 instead of expected 4*4 = 16.


It means that the youngest member of the family - the sister, is only 3 years old.


Then Sam is 3+2 = 5 years old.


Now we know that 


Father + Mother = 73 - 3 - 5 = 65,    and

Father - Mother =  3.


By adding the last two equations, you get  2*Father = 65+3 = 68  ====>  Father is 68/2 = 34 years old.


Then the Mother is  34-3 = 31 years old.
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Solved.