SOLUTION: solve by the substitution method 3x-3y=3 8x+55=y

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Question 145830: solve by the substitution method

3x-3y=3
8x+55=y
Answer by jim_thompson5910(35256) About Me  (Show Source):
You can put this solution on YOUR website!
Start with the given system
3x-3y=3
8x%2B55=y



y=8x%2B55 Rearrange the terms of the second equation




3x-3%288x%2B55%29=3 Plug in y=8x%2B55 into the first equation. In other words, replace each y with 8x%2B55. Notice we've eliminated the y variables. So we now have a simple equation with one unknown.


3x-24x-165=3 Distribute


-21x-165=3 Combine like terms on the left side


-21x=3%2B165Add 165 to both sides


-21x=168 Combine like terms on the right side


x=%28168%29%2F%28-21%29 Divide both sides by -21 to isolate x



x=-8 Divide




Now that we know that x=-8, we can plug this into y=8x%2B55 to find y



y=8%28-8%29%2B55 Substitute -8 for each x


y=-9 Simplify


So our answer is x=-8 and y=-9 which also looks like



Notice if we graph the two equations, we can see that their intersection is at . So this verifies our answer.


+graph%28+500%2C+500%2C+-10%2C+10%2C+-10%2C+10%2C+%283-3x%29%2F%28-3%29%2C+8x%2B55%29+ Graph of 3x-3y=3 (red) and y=8x%2B55 (green)