SOLUTION: How can i solve this system of equation by substitution of -3x-3y=3,y=-5x-7?

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Question 325285: How can i solve this system of equation by substitution of -3x-3y=3,y=-5x-7?
Answer by jim_thompson5910(35256) About Me  (Show Source):
You can put this solution on YOUR website!
-3x-3y=3 Start with the first equation.


-3x-3%28-5x-7%29=3 Plug in y=-5x-7 into the first equation. In other words, replace each y with -5x-7. Notice we've eliminated the y variables. So we now have a simple equation with one unknown.


-3x%2B15x%2B21=3 Distribute


12x%2B21=3 Combine like terms on the left side


12x=3-21Subtract 21 from both sides


12x=-18 Combine like terms on the right side


x=%28-18%29%2F%2812%29 Divide both sides by 12 to isolate x



x=-3%2F2 Reduce



Now that we know that x=-3%2F2, we can plug this into y=-5x-7 to find y


y=-5%28-3%2F2%29-7 Substitute -3%2F2 for each x


y=15%2F2-7 Multiply -5 and -3%2F2 to get 15%2F2


y=1%2F2 Subtract


So the solutions are x=-3%2F2 and y=1%2F2 which form the ordered pair