Resposta:
Arranjo simples:
[tex]\boxed{\sf A_{n,p}=\dfrac{n!}{(n-p)!}}[/tex]
Seja n = 7 e p = 3:
[tex]\sf A_{7,3}=\dfrac{7!}{(7-3)!}[/tex]
[tex]\sf A_{7,3}=\dfrac{7!}{4!}[/tex]
[tex]\sf A_{7,3}=\dfrac{7\cdot6\cdot5\cdot4!}{4!}[/tex]
[tex]\sf A_{7,3}=7\cdot6\cdot5[/tex]
[tex]\red{\sf A_{7,3}=210}[/tex]
