Answer: [B]: " (-6, 9) " .
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Explanation:
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Given the following system of equations:
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x + y = 3 ;
y = 9 ;
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Substitute "9" for "y" in the first equation; to solve for "x"; we already have our value for "y" ; "y = 9 " ; (given) ;
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x + 9 = 3 ;
Subtract "9" from EACH side of the equation;
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x + 9 − 9 = 3 − 9 ;
to get:
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x = -6 .
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Check our answer:
x + y = 3
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-6 + 9 =? 3 ? Yes!
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The answer for the system of equations is:
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x = -6, y = 9 ; or, write as: (-6, 9) .
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which is: Answer choice: [B]: " (-6, 9) " .
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