I'm not even going to bother with the substitution method. Instead of all that, I just want to show you something:
Take the FIRST equation:
y - 2x = 8 Add 2x to each side: y = 8 + 2x
Multiply each side by 2 : 2y = 16 + 4x
Look at that ! The first equation says the same thing as the second one ! Both of them are actually the same equation. You actually have only one equation, with 'x' and 'y' in it. If you graph it, the graph is a straight line, and EVERY point on the line is a solution of the equation.
==> There are an infinite number of solutions, because they only gave you one equation, with two unknown variables. To find a unique solution, you'd need two equations.
