Normally you would expect one solution for x and y, but in this special case, there are an infinite number of solutions because both equations are the same. If you multiply the bottom one with -2, you get:
-2*-2x + -2*7y = -2*-3 simplifies to
4x - 14y = 6, which is the top equation!
If you have one equation with two variables, it is typically not solvable with one set of solutions. x=5 and y=1 is a solution, but so is x=12 and y=3. Those are just two examples.
