$\"\"$

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The elevation changes from $\"\"$ to $\"\"$ .

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Change in elevation = $\"\"$ .

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To subtract an integer , add its opposite.

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Opposite of $\"\"$ is $\"\"$ .

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$\"\"$ (Add $\"\"$ to $\"\"$ )

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

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The change in elevation is $\"\"$ .