simultaneous equation?

- x + y = - 3
2x - y = 0--------ADD

x = - 3

- 3 - y = 3
- 6 = y
y = - 6

x = - 3 , y = - 6

y in terms of x:
x - y = 3
y = x - 3

2x - y = 0
y = 2x

Value of x:
x - 3 = 2x
x = - 3

Value of y (1st equation):
= - 3 - 3
= - 6

Answer: x = - 3, y = - 6

Proof (2nd equation):
2(- 3) - (- 6) = 0
- 6 + 6 = 0
0 = 0

x - y = 3 (solve by using substitution)
2x - y = 0

x - y = 3
x = y + 3

2x - y = 0
2(y + 3) - y = 0
2y + 6 - y = 0
2y - y = -6
y = -6

x - y = 3
x - (-6) = 3
x + 6 = 3
x = 3 - 6
x = -3

∴ x = -3, y = -6

x-y =3
2x-y=0

From first equation
x=3+y
put that in second equation
2(3+y)-y = 0
6+2y-y=0
6+y=0
y= -6

now, x = 3+y
x = 3 + (-6)
x = 3-6
x = -3

Answer
X = -3
Y = -6