Respuesta :

Given

x = -2y

and

x - y = 9

Replace 2nd equation with the 1st:

x - y = 9

(-2y) - y = 9

-2y - y = 9

-3y = 9

y = 9/ -3

y = -3

So, now we know x = -2y, thus

x = -2(-3) = 6

So, the solution is:

(6,-3)

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