有關於折扣的問題(唔明點列條式)

let X be the price of the hangbag

X(1-60%) = 78
X = 78 / 40%
X = 195

設手袋的售價是a元
a*60%=78
a*60%/60%=78/60%
a=78*60分之100
a=130
答:手袋的售價是130元.