okay so you use the bottom to substitute y so your equation will be:
x-1=2x+8 now solve for x
-x-8=-x-8 this is what you will be taking away from both sides
-1-8=2x-x this is your new equation now you just do basic math
-9=x this is x
Now that you found x find y by substituting x
y=2(-9)+8
y= -18+8
y= (-10) this is your y
Now to check your answer on the other equation
y= -9-1
y= (-10) this is now correct
(x,y)form is (-9,-10)
Hopefully i helped out
