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The triangle is equilateral triangle. So all sides are equal.

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Let the side be x.

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Perimeter P = 84.3cm.

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To Find: x.

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\"\"

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\"\"              (Formula for perimeter)

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\"\"         (Substitute: Perimeter P = 84.3cm)

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\"\"                (Add: \"\")\"\"

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\"\"            (Divide each side by 3)

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\"\"                  (Cancel common terms)

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\"\"                    (Divide: \"\")

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The unknown side lengths of the triangle is 28.1cm, 28.1cm and 28.1cm. \"\"

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The unknown side lengths of the triangle is 28.1cm, 28.1cm and 28.1cm.