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

https://learnzillion.com/lessons/3411-simplify-algebraic-expressions-by-combining-like-terms-and-applying-the-distributive-property

Unlike Denominators:

https://www.khanacademy.org/math/arithmetic/fractions/Mixed_number_add_sub/v/adding-mixed-numbers-with-unlike-denominators

Like Denominators:

https://www.khanacademy.org/math/arithmetic/fractions/Mixed_number_add_sub/v/adding-mixed-numbers

Here is a helpful video reviewing the steps/algorithm for dividing decimals:

https://www.khanacademy.org/math/arithmetic/decimals/dividing_decimals/v/dividing-decimals

https://learnzillion.com/lessons/2585-divide-multidigit-decimals-using-the-standard-algorithm