Question 480481
Let Abraham reading speed be x pages per day

So time taken to read 480 pages = 480/x days

No of days required to read 480 pages when 16-page read more on a daily basis= 480/(x+16)

Further it is given that he was able to finish reading the book before 5 days from the same period, hence
(480/x)- {480/(x+16)} = 5

Simplifying above eqn leads to
x^2+16x-1536=0
x^2+48x-32x-1536=0
x(x+48)-32(x+48)=0
(x+48)(x-32)=0
So x = 32 or -48

-48 is not a valid answer

So the correct answer is : reading speed was 32 pages per day which took 15 days to read 480 pages. After increasing speed by 16 pages new speed became 32+16 = 48 pages per day which took 480/48 = 10 days thus he was able to finish reading the book before 5 days from the same period.