He can play 4 rounds. If you find a common denominator, it would end up with 9/12 of an hour to play and then you subtract the 1/12 it took to set it up. this leaves you with 8/12. but, it takes 2/12 of an hour to play each round. so 8 divided by 2 is 4. Which is where the 4 rounds is from!
