Need help on SAT math question?

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1

<p>Can someone explain this to me?</p>

<p>x+y=0
x-y=k</p>

<p>If the ordered pair (1,p) where x=1 and y=p, is a solution of both equations above, then what is the value of k?</p>

<p>The answer is 2.</p>

<p>I don't know how you get that, I keep on getting 0....</p>

2

<p>X=1 , Y=P
plug into the first equation.
(1)+(P)=0
P(or Y) equals -1.
Now use the second equation, using 1 for X and -1 for Y.
(1)-(-1)=2</p>