Answer:
x=4
Explanation:
You put 9x+6y=78 over 3x-6y=-30. Then, you are going to add the two equations. So, you are going to do 9x+3x, 6y-6y (since the second 6 is negative, it ends up subtracting), and 78-30. You will end up canceling the 6y's, and end up with 12x=48. Then, you will divide 48 by 12, and get x=4. Hope this helped:)