數學問題（求定價和售價）

定價:
Let $x be the marked price.
x(30%)=1200
x=1200(100/30)
x=4000
Therefore,the marked price is $4000.

售價:
$4000x(1-30%)
=$4000x70%
=$2800

2006-12-22 22:19:38 補充：
Let $x be the marked price of the washing machine.x(1-95%)=320x(5%)=320x=320(100/5)x=320(20)x=6400Therefore,the marked price of the washing machine is $6400.

設微波焗爐定價是X元。
X(30%)=$1200
X=$1200除30%
X=$4000
售價:
4000x(1-30%)
=$2800

設洗衣機定價是X元。
X(1-95%)=320
X=320除5%
X=$6400
洗衣機定價是6400元。