Resposta:

Explicação passo a passo:

a.

C15,10=

15!/10!(15-10)!=

15!/10!5!=

15.14.13.12.11.10!/10!5!= [corta 10!]

15.14.13.12.11/5.4.3.2.1= [ corta 15 com 5 e 3]

14.13.12.11/4.2=

2184/8=

273

b.

C12,6=

12!/6!(12-6)!=

12!/6!6!=

12.11.10.9.8.7.6!/6!6!= [corta 6!]

12.11.10.9.8.7/6.5.4.3.2.1= [corta 12 com 4 e 3 e 10 com 5 e 2]

11.9.8.7/6=

5544/6=

924

C8,2=

8!/2!(8-2)!=

8!/2!6!=

8.7.6!/2.6!= [corta 6! com 6!]

8.7/2=

56/2=

28

C12,6 + C8,2=

924+28=

952