X=1500（鸭）+2/3×1500（鹅）+4/9X(鸡）X=1500+1000+4/9XX-4/9X=25005/9X=2500X=2500÷5/9X=4500 鸡=4/9X=4/9×4500=500鹅=2/3×1500=1000
