Question

alguém me ajuda por favor ??

Answer 1

Resposta:

(a) 7; (b) 10,5

Explicação passo-a-passo:

(a)

$\dfrac{4}{x}=\dfrac{12}{21}\\\\12x=4\cdot21\\12x=84\\x=\frac{84}{12}\\x=7$

(b)

$\dfrac{9}{x}=\dfrac{12}{14}\\\\12x=9\cdot14\\12x=126\\x=\frac{126}{12}\\x=10,5$