Question 77286
If we have an original square of side x we have the area as:

{{{x*x=x^2}}}

So if we decrease the sides by 2 and it results in a decrease of 36 {{{cm^2}}} we get

{{{(x-2)(x-2)=x^2-36}}}

{{{x^2-4x+4=x^2-36}}} foil the left side

{{{-4x+2=-36}}} Subtract {{{x^2}}} from both sides

{{{-4x=-40}}} Subtract 2 from both sides

{{{x=-40/(-4)}}} Divide both sides by -4

So the original side is
{{{x=10}}}

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Check:
{{{(10-2)(10-2)=(10)^2-36}}} Plug in x=10
{{{(8)(8)=100-36}}}
{{{64=64}}} works