Question

x + y =12 x - y = 2revolver pelo método da substituição dos sistemas

Answer 1

$x+y=12\\x-y=2\\\\x+y=12\\x=12-y\\\\x-y=2\\12-y-y=2\\-y-y=2-12\\-2y=-10\\y=\frac{-10}{-2}\\y=5\\\\x+y=12\\x+5=12\\x=12-5\\x=7\\\\\\S=7,5$

Espero ter ajudado.
Bons estudos! :)