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

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To solve the equations 3x + 4y = 7 and 2y = 6x + 6, the first step is to manipulate the equations to eliminate one variable. By rearranging and combining the equations, it becomes clear that y equals 2. Substituting y back into the first equation allows for the calculation of x. The confusion arose from miscalculating the values during the process. Ultimately, the correct solution for the system of equations leads to the values of x and y being clarified.
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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