Question 1088111
f, father
s, son

"Again, 4 years later,...will be..."-----four years later than now:
{{{system(f-6=7(s-6),f+4=2(s+4))}}}

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{{{f=7s-42+6}}}
{{{f=7s-36}}}
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{{{7s-36+4=2s+8}}}
{{{5s-36+4=8}}}
{{{4s=8-4+36}}}
{{{4s=40}}}
{{{highlight(highlight(s=10))}}}