**Link for Coordinate plane game: http://mrnussbaum.com/flash/StockTheShelves2.0.swf
**Notes on The Real Number System: http://coolmath.com/prealgebra/08-signed-numbers-integers/02-signed-numbers-integers-number-systems-01.htm
**Notes on The Real Number System: http://coolmath.com/prealgebra/08-signed-numbers-integers/02-signed-numbers-integers-number-systems-01.htm