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(08.05)
Which of the following ordered pairs represents the solution to the system given below?

x − 3y = 12
2x + 6y = 60
(0, −4)
(12, 0)
(3, 21)

Respuesta :

I: x-3*y=12
II: 2*x+6*y=60

add I*2 to II:
2*(x-3y)+2x+6y=2*12+60
2x-6y+2x+6y=24+60
4x=84
x=21

insert x=21 into I:
21-3y=12
9-3y=0
9=3y
3=y


is the only solution (21,3), sou you probably have another option which you didn't copy :)

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