Question

determine o valor de X na proporção 9/13=X/26

Answer 1

$\frac{9}{13}=\frac{X}{26}$
$\frac{X}{26}\cdot \:26=\frac{9}{13}\cdot \:26$
$X=18$

Answer 2

Vamos lá :

$\frac{9}{13} = \frac{x}{26} \\ \\ x = \frac{9*26}{13} \\ \\ x = 9 * 2 \\ \\ \boxed{\boxed{x = 18}}$

Logo " x " equivale a 18 .

Espero ter ajudado !!!