n! = n(n-1)(n-2)(n-3)....
∴6! = 6×5×4×3×2×1 = 720
⁸P₅ = [tex] \frac{8!}{(8-5)!} = \frac{8*7*6*5*4*3*2*1}{3*2*1} = 6720[/tex]
¹²C₄ = [tex] \frac{12!}{4!*(12-4)!} = \frac{12*11*10*9*8*7*6*5*4*3*2*1}{4!*8!} [/tex]
= [tex] \frac{12*11*10*9*8*7*6*5*4*3*2*1}{4*3*2*1*8*7*6*5*4*3*2*1} = 495[/tex]
