a: \(\Leftrightarrow\left\{{}\begin{matrix}12x-6y=9\\12x-6y=10\end{matrix}\right.\Leftrightarrow\left(x,y\right)\in\varnothing\)
b: \(\Leftrightarrow\left\{{}\begin{matrix}3x-2y=0\\x+y=10\end{matrix}\right.\)
\(\Leftrightarrow\left\{{}\begin{matrix}3x-2y=0\\2x+2y=20\end{matrix}\right.\Leftrightarrow\left\{{}\begin{matrix}x=4\\y=6\end{matrix}\right.\)
c: \(\Leftrightarrow\left\{{}\begin{matrix}\dfrac{8}{x}+\dfrac{8}{y}=\dfrac{2}{3}\\\dfrac{8}{x}+\dfrac{15}{y}=1\end{matrix}\right.\Leftrightarrow\left\{{}\begin{matrix}-\dfrac{7}{y}=\dfrac{-1}{3}\\\dfrac{1}{x}+\dfrac{1}{y}=\dfrac{1}{12}\end{matrix}\right.\Leftrightarrow\left\{{}\begin{matrix}y=21\\x=28\end{matrix}\right.\)
