Question

$\left \{ {{5x-8y=-9} \atop {y=6-x}} \right.$

Answer 1

5x-8y=-9 (I)
y=6-x     (II)

Substituindo II em I

5x-8(6-x)=-9

5x-48+8x=-9
13x=39
x=3

y=6-3
y=3