SOLUTION: Help please and thank you solve by substitution 3x-y=-15 y=x+1 thanks Heather

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Question 110901: Help please and thank you
solve by substitution
3x-y=-15
y=x+1

thanks
Heather
Answer by jim_thompson5910(35256) About Me  (Show Source):
You can put this solution on YOUR website!
Start with the given system
3x-y=-15
y=x%2B1



3x-%28x%2B1%29=-15 Plug in y=x%2B1 into the first equation. In other words, replace each y with x%2B1. Notice we've eliminated the y variables. So we now have a simple equation with one unknown.


3x-x-1=-15 Distribute the negative


2x-1=-15 Combine like terms on the left side


2x=-15%2B1Add 1 to both sides


2x=-14 Combine like terms on the right side


x=%28-14%29%2F%282%29 Divide both sides by 2 to isolate x



x=-7 Divide




Now that we know that x=-7, we can plug this into y=x%2B1 to find y



y=%28-7%29%2B1 Substitute -7 for each x


y=-6 Simplify


So our answer is x=-7 and y=-6