$\"\"$

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The statement is “ $\"\"$ ”.

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Apply commutative property of addition: $\"\"$ .

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$\"\"$

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$\"\"$ (Add: $\"\"$ )

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Apply associative property of addition: $\"\"$ .

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$\"\"$

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$\"\"$ (Add: $\"\"$ )

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$\"\"$ (Add: $\"\"$ ) $\"\"$

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The sum is $\"\"$ .