Proofreader 1 :
6 hours = 200 pages
1 hour = 200 ÷ 6 = 33 1/3 pages
Proofreader 2:
9 hours = 200 pages
1 hour = 200 ÷ 9 = 22 2/9 pages
Proofreader 1 + Proofreader 2:
1 hour = 33 1/3 + 22 2/9 = 55 5/9
3 hours = 55 5/9 x 3 = 166 2/3
They can read 166 2/3 in 3 hours.
Answer: No, they cannot meet the deadline to read 200 pages in 3 hours.