Question

Sabe-se que x-2y =-7
3x+y= 0, determine x+y

Answer 1

x - 2y = -7 
3x + y = 0  >>>> MULTIPLICA POR 2

Fica:
x - 2y = -7
6x + 2y = 0
----------------------  SOMA
7x = -7
x = -1


3x + y = 0
3(-1) + y = 0
-3 + y = 0
y = 3


x + y =
-1 + 3 =
2

Answer 2

x = 2y-7
3x+y=0
3(2y-7)+y=0
6y-21+y=0
6y+y-21=0
7y= 21
y = 21/7
y = 3

x = 2y-7
x = 2.3-7
x = 6-7
x = -1

x+y = -1+3 = +2