The use of historical and comparative existing data is important to students because it gives them an insight on what they are working on.
Previous datas contains certain informations from which new observations and assessments can be made.
Students uses existing data to compare and contrast different factors like if there was a rise or fall in the system they are working on, the also check if an major changes occurred or things were significantly the same from the past to present.
5p + 2(p + 4) .......because pencil cases (p) sell for 5 bucks a piece....and mechanical pencils (p + 4), sell for 2 bucks a piece. She is basically selling 4 more mechanical pencils then she is pencil cases.
