$\"\"$

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The expression is $\"\"$ .

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The number of combinations formula: $\"\"$ .

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$\"\"$

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

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The fundamental counting principle $\"\"$ .

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$\"\"$

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$\"\"$ (Cancel common terms)

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$\"\"$ (Multiply: $\"\"$ )

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

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= 60 (Multiply: $\"\"$ ) $\"\"$

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The solution is 60.