請問一道數學題

Calculate the total price, including txes, of teach item.
Assume that the PST is calculated only on the price[/COLOR].  (GST 和 PST都是7%）

第一題我是用 (Price x PST + price) x GST + ( Price x PST +Price)得到了正確答案

紅顏色的2句話有區別嗎？

Calculate the total cost of each item assuming a GST of 7% and a PST of 7%, if the PST is calculated on the price of the item plus the GST[/COLOR]

第二題我也用的 (Price x PST + price) x GST + ( Price x PST +Price)卻不對
我自己猜測的用 Price x (PST+GST) + Price 卻得到了正確答案。

為什麼？？

Calculate the total price, including txes, of teach item.Assume that the PST is calculated only on the price.
price+price*(GST+PST)
Calculate the total cost of each item assuming a GST of 7% and a PST of 7%, if the PST is calculated on the price of the item plus the GST
price+price*GST+(price+price*GST)PST
[:794:]  [:810:]  [:450:]

Calculate the total cost of each item assuming a GST of 7% and a PST of 7%, if the PST is calculated on the price of the item plus the GST
price+price*GST+(price+price*GST)PST [:487:]

有沒有人能給我用中文或者英文解釋一下紅句子的不同

GST is calculated only on the price of item BUT PST IS DIFFERENCE.
FIRST RED SENTENCE MEANS THE AMOUNT OF PST equal to  price*GST
second red sentence MEANS THE AMOUNT OF PST equal to (price+price*GST)PST