SOLUTION: systems by elimination 6x-7y=21 3x+7y=6 answer:(3, -3/7) need a full break down of how my book got this answer i understand how they got the 3 but dont understand ho

Algebra ->  Systems-of-equations -> SOLUTION: systems by elimination 6x-7y=21 3x+7y=6 answer:(3, -3/7) need a full break down of how my book got this answer i understand how they got the 3 but dont understand ho      Log On


   

Question 186410: systems by elimination
6x-7y=21
3x+7y=6

answer:(3, -3/7)

need a full break down of how my book got this answer i understand how they got the 3 but dont understand how they got -3/7
Answer by jim_thompson5910(35256) About Me  (Show Source):
You can put this solution on YOUR website!
If you understand how they got the '3' in the ordered pair , then this simply means that they found that x=3


Now pick any equation (I'm going to pick the first one, it doesn't matter which one you choose).


6x-7y=21 Start with the first equation


6%283%29-7y=21 Plug in the previously found solution x=3


18-7y=21 Multiply


-7y=21-18 Subtract 18 from both sides.


-7y=3 Combine like terms.


y=3%2F%28-7%29 Divide both sides by -7 to isolate 'y'


y=-3%2F7 Reduce.


So the other solution is y=-3%2F7 which means that the ordered pair solution is