One person can write 20 pages in 4 hours. The other types 20 pages in 5 hours.
900 pages have to be written by both. They must finish all together.
In these circumstances, how many pages must be distributed to the slower person?
+36916 20 pages/4 hr * x hrs + 20 pages/5hr * x hr = 900 pages
20/4 x + 20/5 x = 900 solve for 'x' the number of hours
then slower (typer) must type 20/5 * x pages .....
