Set up a ratio to find the number of pages read in 80 minutes:
40 pages/ 50 minutes = x pages/ 80 minutes
Cross multiply:
50x = 3200
Divide both sides by 50:
X = 3200/50
X = 64
He will read 64 pages in 80 minutes.
200 -64 = 136
There will be 136 pages left.