Question

7 x + 4y = - 13 linha de baixo - x + y = 5

Answer 1

$\setlength{\columnseprule}{0pt} \begin{cases}7x+4y=-3\\ -x+y=5\end{cases}\\\\\\7x+4(5+x)=-3\\7x+20+4x=-3\\11x=-20-3\\11x=-23\\x=-\dfrac{23}{11}\\\\%===================\raggedcolumns\columnbreak\\%===================y=5+x\\y=5+\left(-\dfrac{23}{11} \right)\\y=5-\dfrac{23}{11}\\y=\dfrac{55-23}{11}\\y=\dfrac{32}{11}$