Signed (Negative) Numbers
Adding and Subtracting Signed Numbers
http://www.khanacademy.org/video/adding-subtracting-negative-numbers?playlist=Pre-algebra
Learn and practice adding and subtracting signed numbers.
Multiplying and Dividing Signed Numbers
http://www.khanacademy.org/video/multiplying-and-dividing-negative-numbers?playlist=Pre-algebra
Learn and practice multiplying and dividing signed numbers.
Adding Signed Decimals
http://www.khanacademy.org/video/adding-real-numbers-with-different-signs?playlist=Developmental%20Math
Learn about adding numbers with different signs.
Adding Signed Fractions
http://www.khanacademy.org/video/adding-fractions-with-different-signs?playlist=Developmental%20Math
Learn about adding fractions with different signs.