Recall the game of chess is played on an 8 by 8 square board and a king can move from a given square to any adjacent square vertically, horizontally or diagonally. What is the maximum number of kings that can be placed on a chessboard without any two of them attacking each other

What is expressed symbolically sum of square between columns?

A store has three types of laptops (A, B, C). There are twice as many type A than type B. There are 20 fewer type A than type C. There are 320 laptops in total. How many laptops are there of each type?

Sessa, an ancient wise man, visited the king of his nation and showed him a new game.  The board was 8 squares by 8 squares.  Two players would be given 16 pieces each, lined up on either side of the board.  The pieces moved in set ways, and the purpose of the game was to move your pieces to trap the King piece of the other player. As you have probably figured out, Sessa invented chess. His king was utterly delighted at the game - war without bloodshed! - and asked Sessa what he would like in return.  In the ancient bombastic style, the King said the request could include up to half of his kingdom.  (That was not meant literally.)  Sessa asked for the game board to be brought before him. "Highness," he said, "I ask for a grain of rice on the first square.  Tomorrow, two grains of rice on the second square.  The day after, 4 grains of rice on the third square.  On the fourth day, 8 grains of rice.  And so on, until the board is full in two months." The king and his ministers laughed…