Question 920709
w=24, d=0, at birth of daughter.


y, number of years to pass.


Now, {{{w+y=3(d+y)}}}.
You first want to find y.
{{{w+y=3d+3y}}}
{{{3d+3y-y-w=0}}}
{{{3d+2y-w=0}}}
{{{2y=w-3d}}}
{{{highlight(y=(w-3d)/2)}}}


substitution of given values,
{{{y=12}}}


Twelve years passed since daughter was born, so daughter is 12 years old.