4x+8(x+y)=4x+8x+8y=12x+8y=480,即y=60-1.5x
4y+9(x+y)=4y+9x+9y=13y+9x=480
把y=60-1.5x代入上式得13（60-1.5x）+9x=480,解得x=200/7 y=120/7