Finding xy from 3x+4y=7 and 2y=6x+6

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    Algebra Algebra 1
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staples82
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If 3x+4y=7 and 2y=6x+6, then what is xy?


3X+4y=7
-6X+2y=6

(2)3X+4y=7 which goes to 6X+8Y=14

I cross the X out, subtract and get 6y=8

then I got 4/3
and final answer i got was 20/3

HOWEVER, the answer says is is -2/3 ... I don't understand how that is the answer...

Please Help!
 
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[tex]\left\{\begin{array}{c} 6x+8y=14 \\ -6x+2y=6 \end{array} \right[/tex]

As i said before,add the two equations,so you'd eliminate "x".

Daniel.
 
oh, my bad ...2, so do I plug it back in, sorry I am going into 7th grade, learning this from a book.

update: ok I understand what you said, now I have y=2...
 
Last edited:
Yes, you are correct that y=2. Now as you said plug it back into find the unknown x.

[tex]3x + 4y = 7[/tex]

You know what to do.

Jameson
 
thank you, dextercioby and Jameson, I understand the problem now.