b: \(\left\{{}\begin{matrix}7x-2y=1\\3x+y=6\end{matrix}\right.\)=>\(\left\{{}\begin{matrix}7x-2y=1\\6x+2y=12\end{matrix}\right.\Leftrightarrow\left\{{}\begin{matrix}13x=13\\3x+y=6\end{matrix}\right.\)=>\(\left\{{}\begin{matrix}x=1\\y=6-3x=6-3=3\end{matrix}\right.\)d: \(\left\{{}\begin{matrix}8x-7y=5\\12x+13y=-8\end{matrix}\right.\)=>\(\left\{{}\begin{matrix}24x-21y=15\\24x+26y=-16\end{matrix}\right.\Leftrightarrow\left\{{}\begin{matrix}-47x=31\\8x-7y=5\end{matrix}\right.\)=>\(\left\{{}\begin{matrix}x=-\dfrac{31}{47}\\7y=8x-5=\dfrac{8\cdot\left(-31\right)}{47}-5=-\dfrac{483}{47}\end{matrix}\right.\)=>\(\left\{{}\begin{matrix}x=-\dfrac{31}{47}\\y=-\dfrac{69}{47}\end{matrix}\right.\)Câu trả lời: b: \(\left\{{}\begin{matrix}7x-2y=1\\3x+y=6\end{matrix}\right.\)=>\(\left\{{}\begin{matrix}7x-2y=1\\6x+2y=12\end{matrix}\right.\Leftrightarrow\left\{{}\begin{matrix}13x=13\\3x+y=6\end{matrix}\right.\)=>\(\left\{{}\begin{matrix}x=1\\y=6-3x=6-3=3\end{matrix}\right.\)d: \(\left\{{}\begin{matrix}8x-7y=5\\12x+13y=-8\end{matrix}\right.\)=>\(\left\{{}\begin{matrix}24x-21y=15\\24x+26y=-16\end{matrix}\right.\Leftrightarrow\left\{{}\begin{matrix}-47x=31\\8x-7y=5\end{matrix}\right.\)=>\(\left\{{}\begin{matrix}x=-\dfrac{31}{47}\\7y=8x-5=\dfrac{8\cdot\left(-31\right)}{47}-5=-\dfrac{483}{47}\end{matrix}\right.\)=>\(\left\{{}\begin{matrix}x=-\dfrac{31}{47}\\y=-\dfrac{69}{47}\end{matrix}\right.\)