-4y+7x=49 -16y+9x=63 x= y=

Since there are 3 books, we can multiply 16 x 3 to get the price. 16 x 3 = 48, and 15% of 48 equals 7.2, because 0.15 x 48 = 7.2. But we are not done yet now, we need to subtract 48 - 7.2 to get our final answer. 48 - 7.2 = 40.8, so 40.8 is our final answer. :)