Question

Resolva os sistemas
X+Y=12
2×-Y=9

Answer 1

x+y= 12
x= 12-y

2x-y= 9
2×(12-y)-y= 9
24-2y-y= 9
-3y= 9-24
-3y= -15 . (-1)
3y= 15
y= 15/3
y= 5

x= 12-y
x= 12-5
x= 7.