$\"\"$

The given expression is $\"\"$ .

$\"\"$ (Combination formula)

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

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

$\"\"$ (Factorial formula $\"\"$ ) \ \ $\"\"$ (Cancel common terms)

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

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

The solution is 15. \ \