Question 818366
x for length, unknown
w for width, unknown and asked to find
p for perimeter, known


{{{x=2w}}}, according to description
{{{2x+2w=p}}}
Using substitution, {{{2(2w)+2w=p}}}
{{{4w+2w=p}}}
{{{6w=p}}}
{{{highlight(w=p/6)}}}