- Subtracting Negative Numbers using a number line - Khan Academy - link
- Defining Rational Numbers, Math is Fun - link
- Irrational Numbers, Math is Fun - link
- Classifying Numbers - Rational and Irrational - Khan Academy link
- Ordering Rational Numbers - Khan Academy link
- How to add, subtract, multiply and divide Rational Numbers, Math is Fun - link, this site has a good description and short step by step video for examples - using variables as well as numbers. At the end of the page is individual practice to help solidify understanding.
- Square Roots, Math is Fun - link