Answer:
a. 72
Step-by-step explanation:
Factorial (!) means take that number and multiply by all the numbers below it to 1
9! = 9*8*7*6*5*4*3*2*1
(9-2)! = 7! = 7*6*5*4*3*2*1
9*8*7*6*5*4*3*2*1
------------------------------
7*6*5*4*3*2*1
Canceling common factors
9*8
------------------------------
1
72
