Question 709245
x is length.  w is width.


{{{x=w+3}}}
AND
{{{2(x+w)=78}}}


FINDING w, WIDTH
{{{highlight(2((w+3)+w)=78)}}}
4w+6=78
w=72/4
w=18


FINDING x, LENGTH
x=w+3
x=18+3
x=21


Summary of dimensions
{{{highlight(x=21)}}},  {{{highlight(w=18)}}}