Question

se alguém conseguir me ajudar ​

Answer 1

$a)\ \frac{12}{4}=\frac{21}{x} \Rightarrow x=7\\\\b)\ \frac{x}{14} = \frac{9}{12} \Rightarrow x=\frac{9*14}{12} = 10.5\\\\c)\ \frac{9}{x} = \frac{9+5}{x+21} \Rightarrow 9*(x+21) = 14*x \Rightarrow 9x+189=14x \Rightarrow x=\frac{189}{5} = 37.8$