Question 1204081
{{{system(v+j=35,v-7=2(j-7))}}}


OR maybe this way:
v and 35-v
{{{v-7=2(35-v-7)}}}


{{{v-7=2(28-v)}}}
{{{v-7=56-2v}}}
{{{3v=56+7}}}
{{{3v=63}}}
{{{highlight(v=21)}}}
and
{{{highlight(35-v=14)}}}


Those two ages differ by 7 years.