✔ 最佳答案
1)
(200-2x)*(1+20%)=x*(1-40%)
(200-2x)*(120%)=x*60%
(200-2x)*1.2=0.6x
240-2.4x=0.6x
240=0.6x+2.4x
240=3x
x=240/3=80
2)
設成本為$x
售價=500*95%=500*0.95=$475
盈利百分率=25%
(售價-成本)/成本*100%=25%
(475-x)/x*100%=25%
(475-x)/x=0.25
475-x=0.25x
475=1.25x
x=380
所以成本為$380