I'd begin by figuring Emmanuel's reading rate. It is 150 pages in 5 hours, which can be re-written as
150 pages 30 pages
--------------- = ---------------
5 hours 1 hour
or 30 pages per hour.
We could then write the equation of two ratios:
30 pages 230 pages
------------- = ----------------
1 hour x
where x represents the length of time required to read 230 pages.
Cross multiplying: (30x pages) = (230 pages)(hour)
Cancel "pages." Then 30x = 230 hours.
Divide both sides by 30: 30x = 230 hours
------- ---------------
30 30
x = 7.6666 hours, or x= 7 2/3 hours
