Substitution method-- ? !
what is the x-coordinate of the solution for the system of equations?

y - x = 9
10 + 2x = -2y

enter your answer in the box.

x=

If you want the x-coordinate of the solution of the system of lineare equations

y - x = 9
10 + 2x = -2y

then you must eliminate y from this sytem.  Rewrite the first equation:  y - x = 9 becomes y = x + 9.  Substitute this (x + 9) for y in  10 + 2x = -2y.  y will now be gone.  Solve the resulting equation for x and you'll be done.