Question 1141154
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...,your age is now one quarter of mine but five years ago it was only one-fifth. How old is the father ?
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f, father
x, son
{{{system(f=4x,x-5=(1/5)(f-5))}}}


{{{5x-25=f-5}}}
{{{5x-25=4x-5}}}
{{{x=25-5}}}
{{{x=20}}}
-
{{{f=4*x}}}
{{{highlight(f=20)}}}