Question

. A Java book is comprised of two
sections core and advanced Java in the
ratio 7:2. How much of each type of
content will be needed to make a book of
450 pages?

Answer 1

Let core java section requires = 7x pages
Advanced java section requires = 2x pages

Total pages = 7x +2x = 9x 
But but total pages = 450
Thus 9x = 450
or x=50

So core java section requires = 7x = 7X50 = 350 pages
Advanced java section requires = 2x = 2X50 = 100 pages

Answer 2

Let the sum of ratios 7x+2x=9x.
core comprises of 7x/9x * 450 = 350 pages.
advances comprises of 2x/9x * 450 = 100 pages.