Question 692842
You are sort of on the right track but you need to make two equations.

Set-Up
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L = length
W = width
Equation 1: {{{46 = 2L + 2W}}}
Equation 2: {{{L = W + 5}}}

Solution:
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Plug (W + 5) into equation 1 for L
Equation 1: {{{46 = 2L + 2W}}}
{{{46 = 2(W+5) + 2W}}} Simplify
{{{46 = 2W + 10 + 2W}}} Combine like terms
{{{46 = 4W + 10}}} Subtract 10 from both sides
{{{36 = 4W}}} Divide both sides by 4
{{{highlight(9 = W)}}}
Now plug 9 into equation 2 for W
Equation 2: {{{L = W + 5}}}
{{{L = (9) + 5}}}
{{{highlight_green(L = 14)}}}