How do you do markdowns and markups

So the book guy mark downed the price of the books by 46%, also known as 0.46.  All decimals are less than 1.  So then, what you do is you take b, which is the variable defining the price of the book, then you multiply it by 0.46.  So the answer of b would be b x 0.46.  For C, you must do 29 x 0.54, and that will give you the answer for C.  Finally, in D, take the answer you got in C, and subtract that by 29.  This will give you your answer.