x,y的和为6
则
x+y=6
y=6-x
把y=6-x代入2x-3y=3k+1,8x-2y=k+3得
2x-18+3x=3k+1
5x-3k=19.(1)
8x-12+2x=k+3
10x-k=15.(2)
(2)-(1)*2得
5k=-23
k=-4.6