a. \(\left\{{}\begin{matrix}x+4y=5\\5x-4y=10\end{matrix}\right.\Leftrightarrow\left\{{}\begin{matrix}6x=15\\x+4y=5\end{matrix}\right.\Leftrightarrow\left\{{}\begin{matrix}x=\dfrac{5}{2}\\y=\dfrac{5}{8}\end{matrix}\right.\)
\(\left\{{}\begin{matrix}\dfrac{5x}{12}+\dfrac{y}{4}=\dfrac{4}{3}\\\dfrac{x}{3}-\dfrac{3y}{4}=\dfrac{47}{12}\end{matrix}\right.\Leftrightarrow\left\{{}\begin{matrix}\dfrac{5}{12}x+\dfrac{1}{4}y=\dfrac{4}{3}\\\dfrac{1}{3}x-\dfrac{3}{4}y=\dfrac{47}{12}\end{matrix}\right.\Leftrightarrow\left\{{}\begin{matrix}\dfrac{5}{4}x+\dfrac{3}{4}y=4\\\dfrac{1}{3}x-\dfrac{3}{4}y=\dfrac{47}{12}\end{matrix}\right.\Leftrightarrow\left\{{}\begin{matrix}\dfrac{19}{12}x=\dfrac{95}{12}\\\dfrac{x}{3}-\dfrac{3y}{4}=\dfrac{47}{12}\end{matrix}\right.\Leftrightarrow\left\{{}\begin{matrix}x=5\\y=-3\end{matrix}\right.\)
