Resposta :
Combinação!
[tex]C_{n,p}=\frac{n!}{(n-p)!p!}\\\\\\C_{7,5}=\frac{7!}{(7-5)!5!}\\\\\\C_{7,5}=\frac{7\cdot6\cdot5!}{2!5!}\\\\\\C_{7,5}=\frac{7\cdot6}{2\cdot1}\\\\\\C_{7,5}=7\cdot3\\\\\\\boxed{C_{7,5}=21}[/tex]
[tex]C_{n,p}=\frac{n!}{(n-p)!p!}\\\\\\C_{7,5}=\frac{7!}{(7-5)!5!}\\\\\\C_{7,5}=\frac{7\cdot6\cdot5!}{2!5!}\\\\\\C_{7,5}=\frac{7\cdot6}{2\cdot1}\\\\\\C_{7,5}=7\cdot3\\\\\\\boxed{C_{7,5}=21}[/tex]