Question 1092493
Dimensions of original rectangle:  x and x-12
Perimeter of original rectangle:  2x+2(x-12)


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Adding 30 units to both dimensions:
{{{2(x+30)+2(x-12+30)=2(2x+2(x-12))}}}
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{{{x+30+x+18=2x+2(x-12)}}}
{{{2x+48=2x+2x-24}}}
{{{48=2x-24}}}
{{{24=x-12}}}
{{{x=36}}}


Original Rectangle:
Length, 36 units
Width, 24 units