①2x+5y-13z=1000
②3x-9y+3z=0
③5x-6y-8z=600
将②除以3得：④x-3y+z=0
①-2×④得：⑤11y-15z=1000
③-5×④得：⑥9y-13z=600
9×⑤-11×⑥得：8z=2400,即⑦z=300
将⑦代入⑥得：⑧y=500
将⑦⑧代入④得：x=1200