Question 1135809
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Let X be the square side length, now unknown.

Then the perimeter is P = 4X, while the area is A = X^2.


They want  A = 4P,   or  X^2 = 4*(4X),  which is the same as  X^2 = 16*X.


Divide by X both sides of the last equation, and you will get


    X = 16.


It is your <U>ANSWER</U> :  The side length must be  16 units long.
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Solved and completed.