Question 352560
let sharon be x years
Peter = x+7
John = 2(x+7)
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Average age = 19 
so sum of their ages = 3*19 = 57
x+x+7+2x+14=57
4x+21=57
4x=57-21
4x=36
x= 9  sharon's age
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peter's age = x+7 = 16
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John's age = 2(x+7)=32

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