The new book was only $19.50 but it was another 60% if the author signed it. what will my book cost with an author's signature. (show your work)

So if you take 10% of $19.50, you have $1.95. If you multiply $1.95 by 6, you get $11.70 which is 60% of the original cost of the book. Add $11.70 to $19.50 and you have $31.20.

The answer is: a = about 63.59ft2 for 15