Ok, so it takes Mike 40 minutes to work on 6 pages. Let's calculate how many he types in 1.5 hours.
In order to calculate that, we'll use a cross product. But first, let's see how many minutes 1.5 hours are correspondent to:
1 hours - 60 minutes
1.5 hours - x
x= 60*1.5 = 90 minutes.
So:
40 min - 6 pages
90 min - x
40x = 6*90
40x = 540
x= 13.5 pages
He will type and spell check 13.5 pages.