Question 1070097
f father
s son
{{{f-5=3(s-5),f+s=110}}}



{{{f-5=3(110-f-5)}}}

{{{f-5=3(105-f)}}}

{{{f-5=315-3f}}}

{{{4f=320}}}

{{{highlight(f=80)}}}
-
{{{highlight(s=30)}}}