Răspuns :
[tex]\it a)\ \ \dfrac{12}{n}=\dfrac{n}{3} \Rightarrow n\cdot n=12\cdot3 =36=6\cdot6 \Rightarrow n=6\\ \\ \\ b)\ \ \dfrac{2n}{7}=\dfrac{14}{n} \Rightarrow 2n\cdot n=14\cdot7 =2\cdot7\cdot7 \Rightarrow n=7[/tex]
[tex]\it a)\ \ \dfrac{12}{n}=\dfrac{n}{3} \Rightarrow n\cdot n=12\cdot3 =36=6\cdot6 \Rightarrow n=6\\ \\ \\ b)\ \ \dfrac{2n}{7}=\dfrac{14}{n} \Rightarrow 2n\cdot n=14\cdot7 =2\cdot7\cdot7 \Rightarrow n=7[/tex]