$\"\"$

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The expression is $\"\"$ .

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Solve the expression.

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$\"\"$ (Permutation formula)

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$\"\"$ (Substitute $\"\"$ and $\"\"$ )

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$\"\"$ (Subtract: $\"\"$ )

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$\"\"$ (Factorial formula $\"\"$ )

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$\"\"$ (Cancel common terms)

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$\"\"$ .

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$\"\"$

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$\"\"$ .