Question 858306
{{{x}}}= number of girls in the class
{{{18}}}= number of boys in the class
We are told that
{{{18=x-w}}}<--->{{{18+w=x}}}
We need to find out the number of students in the class.
We expect that all the boys and girls in the class are students,
and that every students in the class is either a boy or a girl,
so
{{{s=18+x}}}= number of students in the class
substituting {{{18+w}}} for {{{x}}} ,
{{{s=18+(18+w)}}}
{{{s=(18+18)+w}}}
{{{s=highlight(36+w)}}}