because 114 pages are already read and if he needs 333 pages to reach 1/3 of the book you add 114 and 333 so you can find out how much pages is 1/3 of the book. then you multiply that number by 3 because there are 3 sections of 333+114.
Each person shakes 7 hands, but once you count the handshake between A and B, you don't need to count the handshake between B and A. There are a total of 8*7/2 = 28 handshakes.