Resposta:

A)54

B) 90

C)170

D)560

Explicação passo-a-passo:

A)

[tex]d = \frac{n \times (n - 3)}{2} \\ d = \frac{12 \times (12 - 3)}{2} \\ d = \frac{12 \times 9}{2} \\ d = \frac{108}{2} \\ d = 54[/tex]

B)

[tex]d = \frac{15 \times (15 - 3)}{2} \\ d = \frac{15 \times 12}{2} \\ d = \frac{180}{2} \\ d = 90[/tex]

C)

[tex]d = \frac{20 \times (20 - 3)}{2} \\ d = \frac{20 \times 17}{2} \\ d = \frac{340}{2} \\ d = 170[/tex]

D)

[tex]d = \frac{35 \times (35 - 3)}{2} \\ d = \frac{35 \times 32}{2} \\ d = \frac{1120}{2} \\ d = 560[/tex]