Question

{X+y=8}

{5x-2y=5} , então :

Answer 1

{X+y=8 ==> *(2) ↓ ==> y=8-x
{5x-2y=5

{2X+2y=16
{5x-2y=5
-------------- (+)
7x = 21
x = 3 ✓ ===========> y=8-(3) = 5 ✓

Answer 2

$\left \{ \begin{matrix}x+y=8&\\ 5x-2y=5&\end{matrix}\right.$

$x = (8 - y)$ substituindo na segundo logo;

$5(8-y)-2y=5$

$40 -5y-2y=5$

$-7y=-35$

$y=\dfrac{-35}{-7}$

$y=5$

então;

$x+5=8$

$x = 8-5$

$x=3$