Donald Trump purchased a large box of his own books for $55,000. He gave
25 of the books to other republican nominees and then sold the rest on an
Internet website for $63,000, making a profit of $15 on each one.
a) How many his books were in the box?
b) What was the original price of each book?
I'm really lost, I have no idea how to solve this. So I'd appreciate if you could teach me how! It's a practice question for my test tomorrow
b = number of books , p = orig price
b p = 55000
(b - 25)(p + 15) = 63000
... bp + 15b - 25p - 375 = 63000
... 15b - 25p = 8375 ... 3b - 5p = 1675
... 3b = 5p + 1675
3 b p = 165000 ... 5 p^2 + 1675 p = 165000
use quadratic formula to find p
substitute back to find b