设买了鸭肉X千克,则买海鲜85-X
18X+46(85-X)=13.5X+50(85-X)
18X+3910-46X=13.5X+4250-50X
(50+18-46-13.5)X=4250-3910
8.5X=340
X=40(kg)-----------------鸭肉
85-40=45(kg)---------------------海鲜
设买了鸭肉X千克,则买海鲜85-X
18X+46(85-X)=13.5X+50(85-X)
18X+3910-46X=13.5X+4250-50X
(50+18-46-13.5)X=4250-3910
8.5X=340
X=40(kg)-----------------鸭肉
85-40=45(kg)---------------------海鲜