問2 條 f.1 數.20分!

1.The cost of an electrical appliance is $1000.The shop owner marked it at 60% higher than the cost. The shop owner is adjusting the marked price of the electronic appliance such that its selling price will still be the same as the original marked price when it is sold at a 20% discount.Find the percentage increase in the marked price.
答案係25%.

2.The marked price of a bookshelf is 65% higher than its cost. It is known that the bookshelf is sold at 60% off and the discount is $792.Find the percentage loss of the bookshelf.
答案係34%.

我想知WHY和請列式,最好有埋中文意思