Ta có:
\(\dfrac{12}{16}=\dfrac{-x}{4}=\dfrac{21}{y}=\dfrac{z}{80}\)
\(\Rightarrow\left\{{}\begin{matrix}\dfrac{12}{16}=\dfrac{-x}{4}\\\dfrac{12}{16}=\dfrac{21}{y}\\\dfrac{12}{16}=\dfrac{z}{80}\end{matrix}\right.\Rightarrow\left\{{}\begin{matrix}12.4=-x.16\\12.y=21.16\\12.80=z.16\end{matrix}\right.\)
\(\Rightarrow\left\{{}\begin{matrix}x=\dfrac{12.4}{-16}\\y=\dfrac{21.16}{12}\\z=\dfrac{12.80}{16}\end{matrix}\right.\Rightarrow\left\{{}\begin{matrix}x=-3\\y=28\\z=60\end{matrix}\right.\)
Vậy \(\left(x,y,z\right)=\left(-3;28;60\right)\)