Question

8) [7x-11y=23, 21x+2y=-1;​

Answer 1

$\begin{cases} 7x-11y=23\ \ | \cdot (-3) \\ 21x+2y=-1 \end{cases}\\\\\begin{cases} -21x+33y=-69 \\ 21x+2y=-1 \end{cases}\\+--------\\35y=-70\ \ |:35\\ y=-2\\\\7x-11y=2\\ 7x-11*(-2)=23\\7x+22=23\\7x=23-22\\7x=1\ \ |:7\\x=\frac{1}{7}\\\\\begin{cases}x=\frac{1}{7}\\ y=-2 \end{cases}$