Maths questions??

y(1-15%) (1-20%)=selling price
y(1-15%)20%=1360
y(1-15%)=1360/20%
y(1-15%)=1360/0.2
y(1-15%)=6800
y=6800/85%
y=6800/0.85
y=8000


8000*(1-15%)20%
=8000*85%*20%
=6800*20%
=1360


the value of y is 8000.

(1-15%)y is the price of Mr Chan bought the hi-fi
=0.75y
(1-15%)y *(1-20%) is the selling price of Mr Chan sold it to another
=0.75y *0.8
=0.6y

0.75y -0.6y =$1360 佢買回來的價與sell返出去的價的差別為$1360
0.15y =$1360
y =$1360/0.15
y =$9066.67(correct to 2 decimal places) 即是9066又3分2，27200/3

上面那幾位當了Mr Chan sell返出去的價是那個"lost"，
其實是指Mr.Chan由始至終(由買入到賣出)的金錢損失

2007-01-21 15:56:28 補充：
發現計算數值上有錯誤！現在重新回答(1-15%)y is the price of Mr Chan bought the hi-fi=0.85y(1-15%)y *(1-20%) mr.chan賣比人的價=0.85y *0.8=0.68y0.85y -0.68y =$1360 佢買回來的價與sell返出去的價的差別為$13600.17y =$1360y =$1360/0.17y =$8000上面那幾位個ans啱咗，但條式錯了，當了Mr Chan sell返出去的價是那個lost，其實lost是指Mr.Chan由始至終(由買入到賣出)的金錢損失

(85%y)x20%=1360

85%y=6800

y=8000

1360x20%x85%

6800x85%=800

the value is 8000

The value of y is:
yｘ(1－15%)ｘ20%=1360
yｘ85%ｘ20%=1360
y / 85% / 20%=1360
y=1360ｘ100 / 85ｘ100 / 20
y=8000

(a) (85%y)x20%=1360
85%y=6800
y=8000