设牛羊猪单价分别为x,y,z
2x+5y=13z+1000
3x+3z=9y
6y+8z=5x-600
2x+5y-13z=1000
x-3y+z=0
5x-6y-8z=600
2x+5y-13z=1000
2x-6y+2z=0
11y-15z=1000
5x-15y+5z=0
5x-6y-8z=600
9y-13z=600
99y-135z=9000
99y-143z=6600
8z=2400
x=1200
y=500
z=300
牛,羊,猪
1200,500,300