A bookshop is charged $15.40 for a particular book. The shopkeeper wishes to price the book such that his profit would be 30% of his selling price. What should be his selling price?

So first you start with finding 30%, and you do this by entering into a calculator 30 divided by 100 and then times it to the original book price. So:

30 divided by 100 x 15.40 = $4.62

So $4.62 is 30%, meaning all you have to do is take the original price of $15.40 and add the $4.62, so:

$15.40+$4.62 = $20.02