\"\"

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The expression is \"\".

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\"\"               (Substitute x = – 3, y = 8 and z = – 12 in original expression) \"\"

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Additive inverse of  – 8 is 8.

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To subtract – 8, add 8.

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\"\"

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\"\"           (Add: \"\")

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Additive inverse of  – 12 is 12.

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To subtract – 12, add 12.

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\"\"

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

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The simplified expression is 1.