https://www.khanacademy.org/math/cc-sixth-grade-math/cc-6th-factors-and-multiples/cc-6th-gcf/v/lcm-and-gcf-greatest-common-factor–word-problems
Simplifying Expressions Video
Adding Mixed Numbers
Dividing Decimals
Here is a helpful video reviewing the steps/algorithm for dividing decimals:
https://www.khanacademy.org/math/arithmetic/decimals/dividing_decimals/v/dividing-decimals
Dividing With Decimals
Lesson 2: Evaluating Algebraic Expressions
6EE1Evaluating Algebraic Expressions
https://learnzillion.com/lessons/469-evaluate-multiple-step-algebraic-expressions-by-substitution
6EE2B MORE MATH TERMS FOR OPERATIONS
Lesson 1: Exponents and Algebraic Expressions
6EE1 WHOLE NUMBER EXPONENTS
https://learnzillion.com/lessons/460-write-numerical-expressions-involving-wholenumber-exponents
6EE2A READING AND WRITING ALGEBRAIC EXPRESSIONS
https://learnzillion.com/lessons/465-read-and-write-an-algebraic-expression-containing-a-variable