Question

Como resolver o sistema : x+y=12 x-y=8 ?

Answer 1

X=12-y

X-y=8
12-y-y=8
-y-y=8-12
-2y=-4
2y=4
Y=4/2
Y=2

X=12-y
X=12-2
X=10

Answer 2

$\left \{ {{x+y = 12} \atop {x-y = 8}} \right. \\ ---- \\ 2x = 20 \\ x = \frac{20}{2} \\ \boxed{x = 10 } \\ \texttt{agora achamos o valor de y : } \\ x + y = 12 \\ 10 + y = 12 \\ y = 12 - 10 \\ \boxed{y = 2}$