Resources and helpful links...

Purplemath.com- Great for looking up detailed topics in math.

http://www.purplemath.com/modules/systlin1.htm

Glencoe.com- Covers up plenty of math topics in divided chapters.

Wikipedia.com- Certain histories of different subjects. Highly recommended.

http://en.wikipedia.org/wiki/Linear
"Linear." Wikipedia. May 10, 2010. Web. <http://en.wikipedia.org/wiki/Linear>.

Classbrainmath.com- Gives good step-by step procedures and makes everything simple.