F.U.N.? stands for Fluency & Understanding Numbers. In Middle School, the F.U.N.? Empty Number Line can be used to visually represent linear equations, fractions, decimals, percents, negative numbers, as well as many other concepts. Includes number line hardware, activity guide and 543 cards specific to the Common Core Standards for Grades 6-8, and 30 blank write-on/wipe-off cards.