Khan Academy Static

What is "preservation of equality"? Wait, why are we using letters in math? How can an 'x' represent a number? What number is it? I must figure this out!!! Yes, you must. This tutorial is great if you're just beginning to delve into the world of algebraic variables and expressions.

7988_Combining_like_terms.html

7989_Combining_like_terms_challenge_problem.html

7987_Expressions_with_two_variables.html