Question 235469
The perimeter of a rectangle equals 2L + 2W
Equation 1: {{{P = 2*L + 2*W}}}
Equation 2: {{{W = L - 3}}}
Given: P = 22

Solution:
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Plug (L - 3) into equation 1 for W, and 22 for P
{{{P = 2*L + 2*W}}}
{{{22 = 2*L + 2*(L - 3)}}} Rewrite the equation
{{{22 = 2*L + 2*L - 6}}} Combine like terms
{{{22 = 4*L - 6}}} Add 6 to both sides
{{{28 = 4*L}}} Divide both sides by 4
{{{7ft = L}}}

Now plug the 7ft into equation 2 for L
{{{W = L - 3}}}
{{{W = 7 - 3}}}
{{{W = 4ft}}}
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Check your answer using the values in equation 1
{{{P = 2*L + 2*W}}}
{{{22 = 2*7 + 2*4}}}
{{{22 = 14 + 8}}}
{{{22 = 22}}}