A. 3 x + y =9
B. 3x - y =9
C. X - y =9
D. X + 3 y =9

The answer should be D. You’re end equation should be y=-1/3X+3 and to get that from D you should first subtract X which gives you 3y=-X+9 and then divide negative 3 to -X and 9 and you get the answer!