Question 919934
The length: {{{L}}}
the width:{{{W}}}
The perimeter:{{{P=2L+2W}}}
 
if the perimeter of a rectangular sandbox is {{{36ft}}},then

{{{2L+2W=36ft}}}........eq.1

if the length is five times the width, then 

 {{{highlight(L=5W)}}}........eq.2,=> equation representing the length (𝒍 = 𝒍𝒆𝒏𝒈𝒕𝒉)

if you want to find the length and the width, solve the system:

{{{2L+2W=36ft}}}........eq.1
 {{{L=5W}}}........eq.2
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{{{2L+2W=36ft}}}........eq.1.....substitute  {{{5W}}} for  {{{L}}}

{{{2*5W+2W=36ft}}}

{{{10W+2W=36ft}}}

{{{12W=36ft}}}

{{{W=36ft/12}}}

{{{highlight(W=3ft)}}}

go to {{{L=5W}}}........eq.2 substitute  {{{3fy}}} for  {{{W}}}

{{{L=5*3ft}}}

{{{highlight(L=15ft)}}}