a bookstore is offering a discount of 10%. jim wants to buy a book with a RRP of $49.90. how much will it cost him if he pays by cash? how much will it cost him if he pays by credit card

Don't know what you mean by "RRP", but with the discount, Jim will pay $49.90 * .90 = ?

Will Jim still get the discount with a credit card, or possibly is there an even extra charge for using the card?