Question

2y+7x=-5 5y-7x=12
$2y + 7x = - 5 \: \: \\ 5y - 7x = 12$

Answer 1

$\begin{cases}2y + 7x = - 5\\5y - 7x = 12\end{cases}$

+______________

$7y=7\ /:7$

$y=1$

$\begin{cases}2y + 7x = - 5\\ y=1\end{cases}$

$\begin{cases}2 \cdot 1 + 7x = - 5\\ y=1\end{cases}$

$\begin{cases}2 + 7x = - 5\\ y=1\end{cases}$

$\begin{cases} 7x = - 5-2\\ y=1\end{cases}$

$\begin{cases}7x = - 7\ /:7\\ y=1\end{cases}$

$\begin{cases}x = - 1\\ y=1\end{cases}$

Answer 2

Answer: x = -1    y = 1