Answer:
126
Step-by-step explanation:
Using the definition of n [tex]C_{r}[/tex] = n! / r ! (n - r) !
where n ! = n(n - 1)(n - 2) ........ × 3 × 2 × 1
9 [tex]C_{4}[/tex]
= 9 ! / 4 ! 5 ! ← cancel 5 ! on numerator/ denominator
= [tex]\frac{9(8)(7)(6)}{4(3)(2)(1)}[/tex]
= [tex]\frac{3024}{24}[/tex]
= 126
