Solve for xy in Algebra 1: 3x+4y=7 and 2y=6x+6

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The discussion focuses on solving the system of equations 3x + 4y = 7 and 2y = 6x + 6 to find the value of xy. The correct solution involves eliminating x by adding the equations, leading to the conclusion that y = 2. Substituting y back into the first equation allows for the calculation of x, ultimately leading to the product xy = 20/3. The confusion arose from misinterpretation of the steps, but clarification was provided by community members.

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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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You should add them.y=20/10=2.

Daniel.
 
i don't understand...
 
\left\{\begin{array}{c} 6x+8y=14 \\ -6x+2y=6 \end{array} \right

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

Daniel.
 
yeah, then i got 6y=8
 
Why?Don't ypu know what "addition" or "adding" means...?

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.

3x + 4y = 7

You know what to do.

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

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