A student took a system of equations, multiplied the first equation by 2 and the second equation by 3, then added the results together. Based on this, she concluded that there were no solutions. Which system of equations could she have started with?

1) 2x-4y=6
3x+6y=9

2) 3x+y=12
-3x+6y=6

3) -2x+4y=4
-3x+6y=6

4) 3x+6y=9
-2x-4y=4