Question

Me ajudem !!!!!!!!!!

Answer 1

Isola y na primeira e substitui na segunda:

$x+y=18\\2x+y=12\\\\y=18-x\\\\2x-(18-x)=12\\2x-18+x=12\\3x=12+18\\3x=30\\x=\frac{30}{3} \\x=10\\\\y = 18-x\\y=18-10\\y=8$