Vamos là.

Usaremos o teorema de Tales.

a)

3/x = 15/10

15x = 30

x = 2

b)

8/10 = 4/x

8x = 40

x = 5

c)

x/3 = 4/6

6x = 12

x = 2

d)

x/2 = 9/6

6x = 18

x = 3

Olá

A)

[tex]\LARGE{} \dfrac{3}{x} = \dfrac{15}{10} \\ \\ \LARGE{}15x = 30 \\ \\ \LARGE{} \frac{15}{30} \\ \\ \LARGE{}x = 2[/tex]

b)

[tex]\LARGE{} \dfrac{8}{10} = \dfrac{4}{x} \\ \\ \LARGE{}8x = 40 \\ \\ \LARGE{}x = \frac{40}{5} \\ \\ \LARGE{}x = 5[/tex]

c)

[tex]\LARGE{} \frac{x}{3} = \frac{4}{6} \\ \\ \LARGE{}6x = 12 \\ \\ \LARGE{}x = \frac{12}{6} \\ \\ \LARGE{}x = 2[/tex]

d)

[tex]\LARGE{} \frac{x}{2} = \frac{9}{6} \\ \\ \LARGE{}6x = 18 \\ \\ \LARGE{}x = \frac{18}{6} \\ \\ \LARGE{}x = 3[/tex]

[tex]\mathrm{}{\large\boxed{\boxed{  { \large \tt Bons \: \: Estudos}}}}[/tex]

[tex]\large\fbox{Dúvidas Comenta}[/tex]