Question 261906
P = 2L + 2W
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Given: 
P = 22
L = 3W

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{{{22 = 2L + 2W}}}
We can substitute 3W in for L
{{{22 = 2*(3W) + 2W}}}
Simplify
{{{22 = 6W + 2W}}}
Combine like terms
{{{22 = 8W}}}
Divide both sides by 8
{{{highlight(2.75 = W)}}}

L = 3W
L = 3*(2.75)
{{{highlight(L = 8.25)}}}

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Check the answers
P = 2L + 2W
{{{22 = 2*(8.25) + 2*(2.75)}}}
{{{22 = 16.5 + 5.5}}}
{{{highlight(22 = 22)}}}