Question 1003113
x, number of sisters
y, number of brothers


Each brother or sister excludes himself or herself in his or her counting of the other gendered siblings.
{{{system(x=2y-1,y=(2/3)x-1)}}}


The x equation is what the brother says; and the y equation is what the sister says.


Did this interpretation work?
{{{system(x=2y-1,3y=2x-3)}}}


{{{3y=2(2y-1)-3}}}
{{{3y=4y-2-3}}}
{{{3y=4y-5}}}
{{{3y+5=4y-5+5}}}
{{{3y+5=4y}}}
{{{3y+(-3y)+5=4y+(-3y)}}}
{{{highlight(5=y)}}}


Return to the system and take {{{x=2y-1}}}
{{{x=2*5-1}}}
{{{x=10-1}}}
{{{highlight(x=9)}}}


This family has 9 girls (the sisters) and 5 boys (the brothers).