Question

Resolva o sistema presiso pra hj
1x+2y=80
2x+1y=70

Answer 1

1x+2y=80 vezes  (-2)
2x+1y=70

-2x-4y=-160
2x+1y=70

0-3y=-90
y=90/3

y=30


1x+2y=80
1x+2.(30)=80
1x+60=80
1x=80-60
1x=20