Question 388343
let p = unit price of book , q = number of books sold.
sales before was pq.  Under the new unit price 0.75p, 
the new sales is 1.10pq.  We have to solve for x in 1.10pq = 0.75p(q+x).
1.10pq = 0.75pq + 0.75px, or
0.35pq = 0.75px, or 
0.35q = 0.75x, or x = 0.35q/0.75 = 7q/15, the increase in the quantity of books sold, corresponding to a 7*100/15% = 46.67% increase from the previous.