The original price of the book is $39
Mark up is 7.5% . This means there is an increase in price
7.5% increase is 100 + 7.5
= 100 + 7.5
107.5%
To calculate the discount dollar
The mark up price is
107.5/100 x $39
= 1.075 x 39
= $ 41.925
The discount dollar amount = Marked up price - Original price
= $41.925 - $39
= $2.925
The discount dollar amount is $2.925
The selling price is $41.925