Question 861656
Very typical question about rectangle.  I will solve this completely in symbols, generally.


L = length
w = width
k = a given constant.
p = perimeter, a given constant.

The description is as L=w+k, and perimeter, p is given.
This like the generalization, "the length of the rectangle is k more than the width."


Perimeter Equation:
{{{2L+2w=p}}}
{{{2(w+k)+2w=p}}}.
In general, p might or might not be a whole number, and it might or might not be an even number, so I will not immediately here divide both sides by 2.
{{{2w+2k+2w=p}}}
{{{4w+2k=p}}}
{{{4w=p-2k}}}
{{{highlight(w=(p-2k)/4)}}}
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Use the formula for w to find the formula for L.
The description gave L=w+k, so now have {{{L=(p-2k)/4+k}}}, and depending on the kind of form in which you want, can become {{{L=p/4-k/2+k}}}
{{{L=p/4+k-k/2}}}
{{{highlight(L=p/4+k/2)}}}.


Naturally, substitute the given values to compute the values for L and w.