Question 235338
The perimeter of a rectangle is equal to 2L + 2W
Equation 1: {{{2*L + 2*W = 420in}}}
Equation 2: {{{W = L - 4in}}}
Solution:
Plug L-4 into equation 1 for W
{{{2*L + 2*W = 420in}}}
{{{2*L + 2*(L - 4) = 420in}}} rewrite the equation
{{{2*L + 2*L - 8 = 420in}}} Combine like terms
{{{4*L - 8 = 420in}}} Add 8 to both sides
{{{4*L = 428in}}} Divide both sides by 4
{{{L = 107in}}}
The length of the rectangle is 107in.

Check your answer:
Plug 107 into equation 2 for L
{{{W = L - 4in}}}
{{{W = 107 - 4in}}}
{{{W = 103in}}}
Now plug the answers for L and W into equation 1
{{{2*L + 2*W = 420in}}}
{{{2*107 + 2*103 = 420in}}}
{{{214in + 206in = 420in}}}
{{{420in = 420in}}}