How do you solve the system?
y=9-2x
x+5y=0

Well, so the x+5y= 0 you can make this into x=-5y and then plug this in into ( y=9-2x) the -2x , which these would become y=9-2(-5y) simplify and equals to y=9+10y. Then you simplify much smaller y=-9. Now that you have the y number you just plug this in into x=-5y, which these becomes x=-5(-9) and the answer is x=45. At the end you just need to find the x and y, so the answer is x=45 and y=-9      . Hopefully this would make this much easier to you. 

I disagree because if you plug 45 into the x value on y=9-2x you don't get -9. But if x=5 and y= -1 then the equations make sense.

Y=9-2x
-1=9-2(5)
-1=9-10

X+5y=0
5+5(-1)=0
5-5=0