SOLUTION: How do you solve y=4x and y=-x-15 by substitution?

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Question 564692: How do you solve y=4x and y=-x-15 by substitution?
Answer by mananth(16946) About Me  (Show Source):
You can put this solution on YOUR website!
y=4x

y=-x-15
substitute y
4x=-x-15
+x
5x=-15
/5
x=-3
y=4x
y=4*-3
y=-12