Respuesta :

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y = x + 1   (*)

3x - y = 9   (**)

Substitute (*) to (**):

3x - (x + 1) = 9

3x - x - 1 = 9      add 1 to both sides

2x = 10     divide both sides by 2i

x = 5

Put the value of x to (*):

y = 5 + 1

y = 6

Answer: x = 5 and y= 6 → (5, 6).